Method and device for receiving data from asynchronous adjacent cell in wireless communication system

ABSTRACT

A method according to an embodiment of the present invention for receiving, via a terminal, broadcast/multicast data of an asynchronous adjacent cell in a wireless communication system may comprise the steps of: receiving broadcast/multicast transmission schedule information of the asynchronous adjacent cell which is not synchronized with a serving cell of the terminal; and receiving broadcast/multicast data transmitted from the asynchronous adjacent cell on the basis of the broadcast/multicast transmission schedule information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2016/006485, filed on Jun. 17, 2016,which claims the benefit of U.S. Provisional Application No. 62/180,610,filed on Jun. 17, 2015, the contents of which are all herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for receiving broadcast/multicast datafrom an asynchronous neighbor cell (or asynchronous adjacent cell) in awireless communication system supporting a vehicle to everything (V2X)service, and a device supporting the same.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while guaranteeing user activity. Service coverage of mobilecommunication systems, however, has extended even to data services, aswell as voice services, and currently, an explosive increase in traffichas resulted in shortage of resource and user demand for a high speedservices, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive Multiple Input MultipleOutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

An aspect of the present invention provides an efficient method for aterminal to receive broadcast/multicast data from an asynchronousneighbor cell in a wireless communication system.

Another aspect of the present invention provides an efficient method forallowing a terminal to promptly receive a corresponding message withoutdelay even when an asynchronous neighbor cell transmits a warningmessage with high priority, or the like, to be quickly transmitted toeach terminal.

Such an efficient method is also applicable to a wireless communicationsystem supporting a V2X (Vehicle to everything) service.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solution

According to an aspect of the present invention, there is provided amethod for receiving, by a user equipment (UE), broadcast/multicast dataof an asynchronous neighbor cell in a wireless communication system,including: receiving broadcast/multicast transmission scheduleinformation of the asynchronous neighbor cell not synchronized with aserving cell of the UE; and receiving broadcast/multicast datatransmitted from the asynchronous neighbor cell on the basis of thebroadcast/multicast transmission schedule information.

The broadcast/multicast data may be transmitted in a physical downlinkshared channel (PDSCH) related to a demodulation reference signal (DMRS)antenna port from the asynchronous neighbor cell.

The DMRS antenna port and a cell-specific reference signal (CRS) orchannel state information (CSI)-RS may be quasi-co-located(QCL)-assumed.

The broadcast/multicast transmission schedule information may include atleast one of broadcast/multicast transmission timing information of theasynchronous neighbor cell, transmission resource information ofbroadcast/multicast data of the asynchronous neighbor cell, referencesignal (RS) configuration information for demodulatingbroadcast/multicast data, asynchronization related auxiliary informationused for adjust synchronization with the asynchronous neighbor cell, andQCL information.

The step of receiving of the broadcast/multicast transmission scheduleinformation may correspond to a step of receiving first systeminformation of the asynchronous neighbor cell including thebroadcast/multicast transmission schedule information from theasynchronous neighbor cell.

The method for receiving, by the UE, broadcast/multicast data mayfurther include: receiving network (NW) assistance information forassisting the UE to receive the first system information from theserving cell.

The NW assistance information may include at least one of transmissiontiming information of the first system information and updateinformation of the first system information.

The step of receiving the broadcast/multicast transmission scheduleinformation may correspond to a step of receiving the first systeminformation of the asynchronous neighbor cell including thebroadcast/multicast transmission schedule information from the servingcell.

The first system information may be transmitted instead of second systeminformation at a specific timing among timings at which the secondsystem information of the serving cell is transmitted.

The first system information may be transmitted through resourceindependent from resource in which the second system information istransmitted.

The step of receiving the broadcast/multicast transmission scheduleinformation may correspond to a step of receiving a downlink (DL) grantincluding the broadcast/multicast transmission schedule information fromthe serving cell.

The method for receiving, by the UE, broadcast/multicast data mayfurther include: receiving the broadcast/multicast transmission scheduleinformation through the first system information of the asynchronousneighbor cell, without receiving the broadcast/multicast transmissionschedule information through the DL grant during a preset period oftime, after the DL grant is received.

The asynchronous neighbor cell may be determined as at least one cell onthe basis of a radio resource management (RRM) measurement value of theasynchronous neighbor cell.

It may be determined on the basis of an RRM measurement value of theasynchronous neighbor cell and an RRM measurement value of the servingcell.

According to another aspect of the present invention, there is provideda user equipment (UE) for receiving broadcast/multicast data of anasynchronous neighbor cell in a wireless communication system,including: a radio frequency (RF) unit transmitting and receiving aradio signal; and a processor controlling the RF unit, wherein the UEreceives broadcast/multicast transmission schedule information of theasynchronous neighbor cell not synchronized with a serving cell of theUE, and receives broadcast/multicast data transmitted from theasynchronous neighbor cell on the basis of the broadcast/multicasttransmission schedule information.

Advantageous Effects

According to an embodiment of the present invention, since the terminalreceives in advance schedule information related to transmission ofbroadcast/multicast data to be transmitted by an asynchronous neighborcell through system information, the broadcast/multicast data of theasynchronous neighbor cell may be received with low latency.

Also, according to an embodiment of the present invention, since aserving cell provides information regarding a timing at which theterminal may receive system information from the asynchronous neighborcell to the terminal as partial NW-assistance information, it ispossible to assist the terminal to receive broadcast/multicast data.

Also, according to an embodiment of the present invention, since theserving cell provides the partial NW-assistance information generated onthe basis of the transmission schedule information received from theasynchronous neighbor cell to the terminal and the terminal simplyreceives the system information of the asynchronous neighbor cell at atiming indicated by the received partial NW-assistance information,terminal complexity is significantly reduced.

Also, according to an embodiment of the present invention, since theserving cell relays system information received from the asynchronousneighbor cell to the terminal as partial NW-assistance information,there is no need for the terminal to be synchronized with theasynchronous neighbor cell to receive an SIB of the asynchronousneighbor cell, reducing complexity of the terminal.

Also, according to an embodiment of the present invention, since theserving cell may transmit the full NW-assistance information to theterminal and the terminal may immediately receive and decode thebroadcast/multicast data of the asynchronous neighbor cell, an effectthat delay for receiving a signal is reduced may be obtained.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood by aperson skilled in the art to which the present invention pertains, fromthe following detailed description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 5 shows an example of a form in which PUCCH formats are mapped tothe PUCCH region of the uplink physical resource block in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 6 shows the structure of a CQI channel in the case of a normal CPin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 7 shows the structure of an ACK/NACK channel in the case of anormal CP in a wireless communication system to which an embodiment ofthe present invention may be applied.

FIG. 8 shows an example of processing a transport channel of a UL-SCH ina wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 9 shows an example of a process of processing a signal of an uplinkshared channel as a transport channel in a wireless communication systemto which an embodiment of the present invention may be applied.

FIG. 10 shows patterns of reference signals mapped to pairs of downlinkresource blocks in a wireless communication system to which anembodiment of the present invention may be applied.

FIG. 11 shows an uplink subframe including sounding reference signalsymbols in a wireless communication system to which an embodiment of thepresent invention may be applied.

FIG. 12 shows an example of component carriers and carrier aggregationin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 13 shows an example of a structure of a subframe according tocross-carrier scheduling in a wireless communication system to which anembodiment of the present invention may be applied.

FIG. 14 shows one example of generating and transmitting 5 SC-FDMAsymbols during one slot in the wireless communication system to whichthe present invention may be applied

FIG. 15 shows a time-frequency resource block in time-frequency domainsin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 16 shows a process of asynchronous HARQ mode resource allocationand retransmission in a wireless communication system to which anembodiment of the present invention may be applied.

FIG. 17 shows a carrier aggregation-based CoMP system in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 18 shows dividing relay node resource in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 19 shows elements regarding a scheme of direct communicationbetween terminals (D2D).

FIG. 20 shows an embodiment of configuration of resource units.

FIGS. 21 and 22 show V2X communication according to an embodiment of thepresent invention.

FIG. 23 is a flow chart illustrating a V2I communication method of aterminal according to an embodiment of the present invention.

FIG. 24 is a block diagram of a wireless communication device accordingto an embodiment of the present invention.

BEST MODES

Some embodiments of the present invention are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings are intended to describesome exemplary embodiments of the present invention and are not intendedto describe a sole embodiment of the present invention. The followingdetailed description includes more details in order to provide fullunderstanding of the present invention. However, those skilled in theart will understand that the present invention may be implementedwithout such more details.

In some cases, in order to avoid that the concept of the presentinvention becomes vague, known structures and devices are omitted or maybe shown in a block diagram form based on the core functions of eachstructure and device.

In this specification, a base station (BS) (or eNB) has the meaning of aterminal node of a network over which the base station directlycommunicates with a device. In this document, a specific operation thatis described to be performed by a base station may be performed by anupper node of the base station according to circumstances. That is, itis evident that in a network including a plurality of network nodesincluding a base station, various operations performed for communicationwith a device may be performed by the base station or other networknodes other than the base station. The base station (BS) may besubstituted with another term, such as a fixed station, a Node B, an eNB(evolved-NodeB), a Base Transceiver System (BTS), or an access point(AP). Furthermore, the device may be fixed or may have mobility and maybe substituted with another term, such as User Equipment (UE), a MobileStation (MS), a User Terminal (UT), a Mobile Subscriber Station (MSS), aSubscriber Station (SS), an Advanced Mobile Station (AMS), a WirelessTerminal (WT), a Machine-Type Communication (MTC) device, aMachine-to-Machine (M2M) device, or a Device-to-Device (D2D) device.

Hereinafter, downlink (DL) means communication from an eNB to UE, anduplink (UL) means communication from UE to an eNB. In DL, a transmittermay be part of an eNB, and a receiver may be part of UE. In UL, atransmitter may be part of UE, and a receiver may be part of an eNB.

Specific terms used in the following description have been provided tohelp understanding of the present invention, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present invention.

The following technologies may be used in a variety of wirelesscommunication systems, such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), and Non-OrthogonalMultiple Access (NOMA). CDMA may be implemented using a radiotechnology, such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asGlobal System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data rates for GSM Evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of Electricaland Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of a UniversalMobile Telecommunications System (UMTS). 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of an Evolved UMTS(E-UMTS) using evolved UMTS Terrestrial Radio Access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-Advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present invention and that are not described in orderto clearly expose the technical spirit of the present invention may besupported by the documents. Furthermore, all terms disclosed in thisdocument may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A is chieflydescribed, but the technical characteristics of the present inventionare not limited thereto.

General System to which the Present Invention May be Applied

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

3GPP LTE/LTE-A support a radio frame structure type 1 which may beapplicable to Frequency Division Duplex (FDD) and a radio framestructure which may be applicable to Time Division Duplex (TDD).

FIG. 1(a) illustrates the radio frame structure type 1. A radio frameconsists of 10 subframes. One subframe consists of 2 slots in a timedomain. The time taken to send one subframe is called a TransmissionTime Interval (TTI). For example, one subframe may have a length of 1ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in the time domain and includes a pluralityof Resource Blocks (RBs) in a frequency domain. In 3GPP LTE, OFDMsymbols are used to represent one symbol period because OFDMA is used indownlink. An OFDM symbol may be called one SC-FDMA symbol or symbolperiod. An RB is a resource allocation unit and includes a plurality ofcontiguous subcarriers in one slot.

FIG. 1(b) illustrates the frame structure type 2. The radio framestructure type 2 consists of 2 half frames. Each of the half framesconsists of 5 subframes, a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and an Uplink Pilot Time Slot (UpPTS). One subframeconsists of 2 slots. The DwPTS is used for initial cell search,synchronization, or channel estimation in UE. The UpPTS is used forchannel estimation in an eNB and to perform uplink transmissionsynchronization with UE. The guard period is an interval in whichinterference generated in uplink due to the multi-path delay of adownlink signal between uplink and downlink is removed.

In the frame structure type 2 of a TDD system, an uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) to all subframes. Table 1 shows theuplink-downlink configuration.

TABLE 1 Downlink- to- Uplink Uplink- Switch- Downlink point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

Referring to Table 1, in each subframe of the radio frame, “D” isindicative of a subframe for downlink transmission, “U” is indicative ofa subframe for uplink transmission, and “S” is indicative of a specialsubframe including three types of a DwPTS, GP, and UpPTS. Anuplink-downlink configuration may be classified into 7 types. Thepositions and/or number of downlink subframes, special subframes, anduplink subframe are different in each configuration.

A point of time at which a change is performed from downlink to uplinkor a point of time at which a change is performed from uplink todownlink is called a switching point. The periodicity of the switchingpoint means a cycle in which an uplink subframe and a downlink subframeare changed is identically repeated. Both 5 ms and 10 ms are supportedin the periodicity of a switching point. If the periodicity of aswitching point has a cycle of a 5 ms downlink-uplink switching point,the special subframe S is present in each half frame. If the periodicityof a switching point has a cycle of a 5 ms downlink-uplink switchingpoint, the special subframe S is present in the first half frame only.

In all the configurations, 0 and 5 subframes and a DwPTS are used foronly downlink transmission. An UpPTS and a subframe subsequent to asubframe are always used for uplink transmission.

Such uplink-downlink configurations may be known to both an eNB and UEas system information. An eNB may notify UE of a change of theuplink-downlink allocation state of a radio frame by transmitting onlythe index of uplink-downlink configuration information to the UEwhenever the uplink-downlink configuration information is changed.Furthermore, configuration information is kind of downlink controlinformation and may be transmitted through a Physical Downlink ControlChannel (PDCCH) like other scheduling information. Configurationinformation may be transmitted to all UEs within a cell through abroadcast channel as broadcasting information.

Table 2 below shows a configuration (length of DwPTS/GP/UpPTS) of aspecial subframe.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix in UpPTSdownlink Normal UpPTS cyclic Extended Normal Extended Special prefixcyclic cyclic cyclic subframe in prefix prefix in prefix inconfiguration DwPTS uplink in uplink DwPTS uplink uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of a radio frame is only one example. The number ofsubcarriers included in a radio frame or the number of slots included ina subframe and the number of OFDM symbols included in a slot may bechanged in various ways.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

Referring to FIG. 2, one downlink slot includes a plurality of OFDMsymbols in a time domain. It is described herein that one downlink slotincludes 7 OFDMA symbols and one resource block includes 12 subcarriersfor exemplary purposes only, and the present invention is not limitedthereto.

Each element on the resource grid is referred to as a resource element,and one resource block (RB) includes 12×7 resource elements. The numberof RBs N^(DL) included in a downlink slot depends on a downlinktransmission bandwidth.

The structure of an uplink slot may be the same as that of a downlinkslot.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 3, a maximum of three OFDM symbols located in a frontportion of a first slot of a subframe correspond to a control region inwhich control channels are allocated, and the remaining OFDM symbolscorrespond to a data region in which a physical downlink shared channel(PDSCH) is allocated. Downlink control channels used in 3GPP LTEinclude, for example, a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), and a physicalhybrid-ARQ indicator channel (PHICH).

A PCFICH is transmitted in the first OFDM symbol of a subframe andcarries information about the number of OFDM symbols (i.e., the size ofa control region) which is used to transmit control channels within thesubframe. A PHICH is a response channel for uplink and carries anacknowledgement (ACK)/not-acknowledgement (NACK) signal for a HybridAutomatic Repeat Request (HARQ). Control information transmitted in aPDCCH is called Downlink Control Information (DCI). DCI includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for aspecific UE group.

A PDCCH may carry information about the resource allocation andtransport format of a downlink shared channel (DL-SCH) (this is alsocalled an “downlink grant”), resource allocation information about anuplink shared channel (UL-SCH) (this is also called a “uplink grant”),paging information on a PCH, system information on a DL-SCH, theresource allocation of a higher layer control message, such as a randomaccess response transmitted on a PDSCH, a set of transmission powercontrol commands for individual UE within specific UE group, and theactivation of a Voice over Internet Protocol (VoIP), etc. A plurality ofPDCCHs may be transmitted within the control region, and UE may monitora plurality of PDCCHs. A PDCCH is transmitted on a single ControlChannel Element (CCE) or an aggregation of some contiguous CCEs. A CCEis a logical allocation unit that is used to provide a PDCCH with acoding rate according to the state of a radio channel. A CCE correspondsto a plurality of resource element groups. The format of a PDCCH and thenumber of available bits of a PDCCH are determined by an associationrelationship between the number of CCEs and a coding rate provided byCCEs.

An eNB determines the format of a PDCCH based on DCI to be transmittedto UE and attaches a Cyclic Redundancy Check (CRC) to controlinformation. A unique identifier (a Radio Network Temporary Identifier(RNTI)) is masked to the CRC depending on the owner or use of a PDCCH.If the PDCCH is a PDCCH for specific UE, an identifier unique to the UE,for example, a Cell-RNTI (C-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for a paging message, a paging indication identifier, forexample, a Paging-RNTI (P-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for system information, more specifically, a SystemInformation Block (SIB), a system information identifier, for example, aSystem Information-RNTI (SI-RNTI) may be masked to the CRC. A RandomAccess-RNTI (RA-RNTI) may be masked to the CRC in order to indicate arandom access response which is a response to the transmission of arandom access preamble by UE.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 4, the uplink subframe may be divided into a controlregion and a data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) carrying uplink control information is allocatedto the control region. A physical uplink shared channel (PUSCH) carryinguser data is allocated to the data region. In order to maintain singlecarrier characteristic, one UE does not send a PUCCH and a PUSCH at thesame time.

A Resource Block (RB) pair is allocated to a PUCCH for one UE within asubframe. RBs belonging to an RB pair occupy different subcarriers ineach of 2 slots. This is called that an RB pair allocated to a PUCCH isfrequency-hopped in a slot boundary.

Physical Uplink Control Channel (PUCCH)

The Uplink Control Information (UCI) transmitted through a PUCCH mayinclude Scheduling Request (SR), HARQ ACK/NACK information, and downlinkchannel measurement information as shown below.

-   -   SR (Scheduling Request): used for requesting uplink UL-SCH        resources. SR is transmitted by On-Off Keying (OOK) scheme.    -   HARQ ACK/NACK: a signal responding to a downlink data packet on        a PDSCH. This signal indicates whether a downlink data packet        has successfully received or not. ACK/NACK 1 bit is transmitted        in response to a single downlink codeword while ACK/NACK 2 bits        are transmitted in response to two downlink codewords.    -   CSI (Channel State Information): feedback information about a        downlink channel. CSI may include at least one of a Channel        Quality Indicator (CQI), a Rank Indicator (RI), a Precoding        Matrix Indicator (PMI), and a Precoding Type Indicator (PTI).        For each subframe, 20 bits are used to represent the CSI.

HARQ ACK/NACK information may be generated depending on whether adownlink data packet on a PDSCH has been successfully decoded. In anexisting wireless communication system, 1 bit is transmitted as ACK/NACKinformation with respect to the transmission of downlink singlecodeword, and 2 bits are transmission as ACK/NACK information withrespect to the transmission of downlink 2 codewords.

Channel measurement information denotes feedback information related toa Multiple Input Multiple Output (MIMO) scheme and may include a ChannelQuality Indicator (CQI), a Precoding Matrix Index (PMI), and a RankIndicator (RI). Such channel measurement information may be commonlycalled a CQI.

In order to transmit a CQI, 20 bits may be used in each subframe.

A PUCCH may be modulated using a Binary Phase Shift Keying (BPSK) schemeand a Quadrature Phase Shift Keying (QPSK) scheme. Control informationfor a plurality of UEs may be transmitted through a PUCCH. If CodeDivision Multiplexing (CDM) is performed in order to distinguish thesignals of UEs from each other, a Constant Amplitude ZeroAutocorrelation (CAZAC) sequence of a length 12 is mostly used. TheCAZAC sequence has a characteristic in that a constant size (amplitude)is maintained in a time domain and a frequency domain. Accordingly, theCAZAC sequence has a property suitable for increasing coverage bylowering the Peak-to-Average Power Ratio (PAPR) or Cubic Metric (CM) ofUE. Furthermore, ACK/NACK information about downlink data transmissiontransmitted through a PUCCH is covered using an orthogonal sequence oran Orthogonal Cover (OC).

Furthermore, control information transmitted through a PUCCH may bedistinguished from each other using a cyclically shifted sequence havinga different Cyclic Shift (CS) value. The cyclically shifted sequence maybe generated by cyclically shifting a base sequence by a specific CSamount. The specific CS amount is indicated by a CS index. The number ofavailable CSs may be different depending on delay spread of a channel. Avariety of types of sequences may be used as the base sequence, and theCAZAC sequence is an example of the sequences.

Furthermore, the amount of control information that may be transmittedby UE in one subframe may be determined depending on the number ofSC-FDMA symbols which may be used to send the control information (i.e.,SC-FDMA symbols other than SC-FDMA symbols which are used to send aReference Signal (RS) for the coherent detection of a PUCCH).

In a 3GPP LTE system, a PUCCH is defined as a total of 7 differentformats depending on control information that is transmitted, amodulation scheme, and the amount of control information. The attributesof Uplink Control Information (UCI) transmitted according to each PUCCHformat may be summarized as in Table 2 below.

TABLE 3 PUCCH Format Uplink Control Information (UCI) Format 1Scheduling Request(SR)(unmodulated waveform) Format 1a 1-bit HARQACK/NACK with/without SR Format 1b 2-bit HARQ ACK/NACK with/without SRFormat 2 CQI (20 coded bits) Format 2 CQI and 1- or 2-bit HARQ ACK/NACK(20 bits) for extended CP only Format 2a CQI and 1-bit HARQ ACK/NACK(20 + 1 coded bits) Format 2b CQI and 2-bit HARQ ACK/NACK (20 + 2 codedbits) Format 3 HARQ ACK/NACK, SR, CSI (48 coded bits)

The PUCCH format 1 is used for SR-only transmission. In the case ofSR-only transmission, a not-modulated waveform is applied. This isdescribed in detail later.

The PUCCH format 1a or 1b is used to send HARQ ACK/NACK. If HARQACK/NACK is solely transmitted in a specific subframe, the PUCCH format1a or 1b may be used. Alternatively, HARQ ACK/NACK and an SR may betransmitted in the same subframe using the PUCCH format 1a or 1b.

PUCCCH format 2 is used for transmission of CQI, and PUCCH format 2a or2b is used for transmission of CQI and HARQ ACK/NACK. In the case ofextended CP, PUCCH format 2 may be used for transmission of CQI and HARQACK/NACK.

PUCCH format 3 is used for carrying an encoded UCI of 48 bits. PUCCHformat 3 may carry HARQ ACK/NACK about a plurality of serving cells, SR(if exists), and a CSI report about one serving cell.

FIG. 5 shows an example of a form in which the PUCCH formats are mappedto the PUCCH region of the uplink physical resource block in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

In FIG. 5, N_RB{circumflex over ( )}UL is indicative of the number ofRBs in uplink, and 0, 1, . . . , N_RB{circumflex over ( )}UL−1 means thenumber of physical RBs. Basically, a PUCCH is mapped to both edges of anuplink frequency block. As shown in FIG. 5, the PUCCH format 2/2a/2b ismapped to a PUCCH region indicated by m=0, 1. This may represent thatthe PUCCH format 2/2a/2b is mapped to RBs located at a band edge.Furthermore, the PUCCH format 2/2a/2b and the PUCCH format 1/1a/1b maybe mixed and mapped to a PUCCH region indicated by m=2. Furthermore, thePUCCH format 1/1a/1b may be mapped to a PUCCH region indicated by m=3,4, 5. UEs within a cell may be notified of the number (N_RB{circumflexover ( )}(2)) of PUCCH RBs which may be used by the PUCCH format 2/2a/2bthrough broadcasting signaling.

The PUCCH format 2/2a/2b is described below. The PUCCH format 2/2a/2b isa control channel for transmitting channel measurement feedback (i.e., aCQI, a PMI, and an RI).

The report cycle of channel measurement feedback (hereinafter commonlycalled “CQI information”) and a frequency unit (or frequency resolution)to be measured may be controlled by an eNB. In a time domain, a periodicor aperiodic CQI report may be supported. The PUCCH format 2 may be usedfor a periodic report, and a PUSCH may be used for an aperiodic report.In the case of an aperiodic report, an eNB may instruct UE to carry anindividual CQI report on a resource scheduled to transmit uplink data.

FIG. 6 shows the structure of a CQI channel in the case of a normal CPin a wireless communication system to which an embodiment of the presentinvention may be applied.

The SC-FDMA symbols 1 and 5 (i.e., the second and the sixth symbols) ofthe SC-FDMA symbols 0 to 6 of one slot are used to transmit ademodulation reference signal (DMRS), and the remaining SC-FDMA symbolsof the SC-FDMA symbols 0 to 6 of the slot may be used to CQIinformation. Meanwhile, in the case of an extended CP, one SC-FDMAsymbol (SC-FDMA symbol 3) is used for DMRS transmission.

In the PUCCH format 2/2a/2b, modulation by a CAZAC sequence issupported, and a QPSK-modulated symbol is multiplied by a CAZAC sequenceof a length 12. A Cyclic Shift (CS) of the sequence is changed between asymbol and a slot. Orthogonal covering is used for a DMRS.

A reference signal (DMRS) is carried on 2 SC-FDMA symbols that belong to7 SC-FDMA symbols included in one slot and that is spaced at 3 SC-FDMAsymbols. CQI information is carried on the remaining 5 SC-FDMA symbolsof the 7 SC-FDMA symbols. Two RSs are used in one slot in order tosupport high-speed UE. Furthermore, UEs are distinguished from eachother using Cyclic Shift (CS) sequences. CQI information symbols aremodulated into all SC-FDMA symbols and transferred. The SC-FDMA symbolsconsist of one sequence. That is, UE modulates a CQI using each sequenceand sends the CQI.

The number of symbols which may be transmitted in one TI is 10, and themodulation of CQI information is determined up to QPSK. If QPSK mappingis used for an SC-FDMA symbol, a CQI value of 10 bits may be carried onone slot because a CQI value of 2 bits may be carried on the SC-FDMAsymbol. Accordingly, a CQI value having a maximum of 20 bits may becarried on one subframe. Frequency domain spread code is used to spreadCQI information in a frequency domain.

A CAZAC sequence (e.g., ZC sequence) of a length 12 may be used as thefrequency domain spread code. Control channels may be distinguished fromeach other by applying CAZAC sequences having different cyclic shiftvalues. IFFT is performed on frequency domain-spread CQI information.

12 different UEs may be subjected to orthogonal multiplexing on the samePUCCH RB by 12 cyclic shifts having the same interval. In the case of anormal CP, a DMRS sequence on the SC-FDMA symbols 1 and 5 (on an SC-FDMAsymbol 3 in the case of an extended CP) are similar to a CQI signalsequence on a frequency domain, but modulation, such as CQI information,is not applied to the DMRS sequence.

UE may be semi-statically configured by higher layer signaling so thatit periodically reports different CQI, PMI and RI Types on PUCCHresources indicated by PUCCH resource indices

$n_{PUCCH}^{({1,\overset{\sim}{p}})},n_{PUCCH}^{({2,\overset{\sim}{p}})},$and

$n_{PUCCH}^{({3,\overset{\sim}{p}})}.$In this case, the PUCCH resource index

$n_{PUCCH}^{({2,\overset{\sim}{p}})}$is information indicative of a PUCCH region that is used to transmit thePUCCH format 2/2a/2b and the value of a Cyclic Shift (CS) to be used.

Hereinafter, the PUCCH format 1a and 1b is described below.

In the PUCCH format 1a/1b, a symbol modulated using a BPSK or QPSKmodulation scheme is multiplied by a CAZAC sequence of a length 12. Forexample, the results of a modulation symbol d(0) by a CAZAC sequencer(n)(n=0, 1, 2, . . . , N−1) of a length N become y(0), y(1), y(2), . .. , y(N−1). The symbols y(0), . . . , y(N−1) may be called a block ofsymbols. After the modulation symbol is multiplied by the CAZACsequence, block-wise spread using an orthogonal sequence is applied.

A Hadamard sequence of a length 4 is used for common ACK/NACKinformation, and a Discrete Fourier Transform (DFT) sequence of a length3 is used for shortened ACK/NACK information and a reference signal.

In the case of an extended CP, a Hadamard sequence of a length 2 is usedin a reference signal.

FIG. 7 shows the structure of an ACK/NACK channel in the case of anormal CP in a wireless communication system to which an embodiment ofthe present invention may be applied.

FIG. 7 illustrates a PUCCH channel structure for transmitting HARQACK/NACK without a CQI.

A Reference Signal (RS) is carried on 3 contiguous SC-FDMA symbol thatbelong to 7 SC-FDMA symbols included in one slot and that are placed ina middle portion, and an ACK/NACK signal is carried on the remaining 4SC-FDMA symbols of the 7 SC-FDMA symbols.

Meanwhile, in the case of an extended CP, an RS may be carried on 2contiguous symbols placed in the middle of one slot. The number andpositions of symbols used in an RS may be different depending on controlchannels, and the number and positions of symbols used in an ACK/NACKsignal associated with the control channels may be changed depending onthe number and positions of symbols used in the RS.

ACK information (not-scrambled state) of 1 bit and 2 bits may berepresented as one HARQ ACK/NACK modulation symbol using respective BPSKand QPSK modulation schemes. Positive ACK (ACK) may be encoded as “1”,and negative ACK (NACK) may be encoded as “0”.

When a control signal is to be transmitted within an allocatedbandwidth, two-dimensional spreading is applied in order to increasemultiplexing capacity. That is, in order to increase the number of UEsor the number of control channels that may be multiplexed, frequencydomain spreading and time domain spreading are used at the same time.

In order to spread an ACK/NACK signal in a frequency domain, a frequencydomain sequence is used as a base sequence. A Zadoff-Chu (ZC) sequencewhich is one of CAZAC sequences, may be used as the frequency domainsequence. For example, by applying a different Cyclic Shift (CS) to a ZCsequence which is a base sequence, different UEs or different controlchannels may be multiplexed. The number of CS resources supported in aSC-FDMA symbol for PUCCH RBs for transmitting HARQ ACK/NACK isconfigured by a cell-specific upper layer signaling parameterΔ_shift{circumflex over ( )}PUCCH.

An ACK/NACK signal spread in a frequency domain is spread in a timedomain using orthogonal spreading code. A Walsh-Hadamard sequence or DFTsequence may be used as the orthogonal spreading code. For example, anACK/NACK signal may be spread for 4 symbols using an orthogonal sequencew0, w1, w2, or w3 of a length 4. Furthermore, an RS is also spread usingan orthogonal sequence of a length 3 or length 2. This is calledOrthogonal Covering (OC).

A plurality of UEs may be multiplexed using a Code Division Multiplexing(CDM) method using CS resources in a frequency domain and OC resourcesin a time domain, such as those described above. That is, ACK/NACKinformation and RSs of a large number of UEs may be multiplexed on thesame PUCCH RB.

The number of spreading code supported for ACK/NACK information isrestricted by the number of RS symbols with respect to such time domainspreading CDM. That is, the multiplexing capacity of an RS is smallerthan the multiplexing capacity of ACK/NACK information because thenumber of SC-FDMA symbols for RS transmission is smaller than the numberof SC-FDMA symbols for ACK/NACK information transmission.

For example, in the case of a normal CP, ACK/NACK information may betransmitted in 4 symbols. 3 pieces of orthogonal spreading code not 4are used for ACK/NACK information. The reason for this is that only 3pieces of orthogonal spreading code may be used for an RS because thenumber of symbols for RS transmission is limited to 3.

In case that 3 symbols of one slot may be used for RS transmission and 4symbols of the slot may be used for ACK/NACK information transmission ina subframe of a normal CP, for example, if 6 Cyclic Shifts (CSs) may beused in a frequency domain and 3 Orthogonal Cover (OC) resources may beused in a time domain, HARQ ACK from a total of 18 different UEs may bemultiplexed within one PUCCH RB. In case that 2 symbols of one slot areused for RS transmission and 4 symbols of one slot are used for ACK/NACKinformation transmission in a subframe of an extended CP, for example,if 6 CSs may be used in a frequency domain and 2 OC resources may beused in a time domain, HARQ ACK from a total of 12 different UEs may bemultiplexed within one PUCCH RB.

The PUCCH format 1 is described below. A Scheduling Request (SR) istransmitted in such a way as to make a request or does not make arequest that UE is scheduled. An SR channel reuses an ACK/NACK channelstructure in the PUCCH format 1a/1b and consists of an On-Off Keying(OKK) method based on an ACK/NACK channel design. An RS is nottransmitted in the SR channel. Accordingly, a sequence of a length 7 isused in the case of a normal CP, and a sequence of a length 6 is used inthe case of an extended CP. Different cyclic shifts or orthogonal coversmay be allocated to an SR and ACK/NACK. That is, in order to send apositive SR, UE sends HARQ ACK/NACK through a resource allocated for theSR. In order to send a negative SR, UE sends HARQ ACK/NACK through aresource allocated for ACK/NACK.

An enhanced-PUCCH (e-PUCCH) format is described below. An e-PUCCH maycorrespond to the PUCCH format 3 of an LTE-A system. A block spreadingtechnique may be applied to ACK/NACK transmission using the PUCCH format3.

The block spreading technique will be described in detail with referenceto FIG. 14 hereinafter.

PUCCH Piggybacking

FIG. 8 shows an example of transport channel processing for an UL-SCH ina wireless communication system to which an embodiment of the presentinvention may be applied.

In a 3GPP LTE system (=E-UTRA, Rel. 8), in the case of UL, in order toefficiently use the power amplifier of UE, a Peak-to-Average Power Ratio(PAPR) characteristic or Cubic Metric (CM) characteristic affectingperformance of the power amplifier are set to maintain good singlecarrier transmission. That is, in the case of PUSCH transmission in anexisting LTE system, the single carrier characteristic of data may bemaintained through DFT-precoding. In the case of PUCCH transmission, asingle carrier characteristic may be maintained by carrying informationon a sequence having a single carrier characteristic and sending theinformation. However, if DFT-precoded data is discontiguously allocatedbased on a frequency axis, or a PUSCH and a PUCCH are transmitted at thesame time, such a single carrier characteristic is not maintained.Accordingly, if PUSCH transmission is to be performed in the samesubframe as that of PUCCH transmission as in FIG. 11, Uplink ControlInformation (UCI) information to be transmitted through a PUCCH istransmitted (piggybacked) along with data through a PUSCH in order tomaintain the single carrier characteristic.

In a subframe in which a PUSCH is transmitted, a method of multiplexingUplink Control Information (UCI) (a CQI/PMI, HARQ-ACK, an RI, etc.) witha PUSCH region is used because existing LTE UE is unable to send a PUCCHand a PUSCH at the same time as described above.

For example, if a Channel Quality Indicator (CQI) and/or a PrecodingMatrix Indicator (PMI) are to be transmitted in a subframe allocated tosend a PUSCH, UL-SCH data and the CQI/PMI may be multiplexed prior toDFT-spreading and may be transmitted along with control information anddata. In this case, the UL-SCH data is subjected to rate matching bytaking the CQI/PMI resources into consideration. Furthermore, a methodof puncturing the UL-SCH data into control information, such as HARQACK, and an RI, and multiplexing the results with a PUSCH region isused.

FIG. 9 shows an example of a signal processing process in an uplinkshared channel, that is, a transport channel, in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Hereinafter, a signal processing process for an uplink shared channel(hereinafter called an “UL-SCH”) may be applied to one or more transportchannels or control information types.

Referring to FIG. 9, an UL-SCH transfers data to a coding unit in theform of a Transport Block (TB) once for each Transmission Time Interval(TII).

CRC parity bits P_0˜P_L−1 are attached to the bits a_0˜a_A−1 of thetransport block received from a higher layer at step S90. In this case,A is the size of the transport block, and L is the number of paritybits. The input bits to which the CRC parity bits have been attached areb_0˜b_B−1. In this case, B is indicative of the number of bits of thetransport block including the CRC parity bits.

The input bits b_0˜b_B−1 are segmented into several Code Blocks (CBs)based on the TB size. A CRC is attached to the segmented several CBs atstep S91. Bits after the segmentation of the CBs and the attachment ofthe CRC are c_r0˜c_r(Kr−1). In this case, r is a CB number (r=0, . . . ,C−1), and Kr is the number of bits according to a CB r. Furthermore, Cis a total number of CBs.

Next, channel coding is performed at step S92. Output bits after thechannel coding are d_r0{circumflex over ( )}(i)˜d_r(Dr−1) {circumflexover ( )}(i). In this case, i is a coded stream index and may have avalue 0, 1, or 2 value. D_(r) is the number of bits of the i-th-codedstream for the CB r. r is a CB number (r=0, . . . , C−1), and C a totalnumber of CBs. Each CB may be coded by turbo coding.

Next, rate matching is performed at step S93. Bits after the ratematching are e_r0˜e_r(Er−1). In this case, r is a CB number (r=0, . . ., C−1), and C is a total number of CBs. E, is the number of bits of ar-th code block that has been subjected to rate matching.

Next, a concatenation between the CBs is performed again at step S94.Bits after the concatenation of the CBs are f_0˜f_G−1. In this case, Gis a total number of coded bits for transmission. When controlinformation is multiplexed with UL-SCH transmission, the number of bitsused for control information transmission is not included.

Meanwhile, when control information is transmitted in a PUSCH, channelcoding is independently performed on a CQI/PMI, an RI, and ACK/NACK,that is, the control information, at steps S96, S97, and S98. The piecesof control information have different coding rates because differentcoded symbols are allocated for the transmission of the controlinformation.

In Time Division Duplex (TDD), ACK/NACK feedback mode supports two typesof ACK/NACK bundling mode and ACK/NACK multiplexing mode by theconfiguration of a higher layer. For ACK/NACK bundling, ACK/NACKinformation bits include 1 bit or 2 bits. For ACK/NACK multiplexing,ACK/NACK information bits include 1 bit to 4 bits.

After the concatenation between the CBs at step S134, the multiplexingof the coded bits f_0˜f_G−1 of the UL-SCH data and the coded bitsq_0˜q_(N_L*Q_CQI−1) of the CQI/PMI are performed at step S95. Theresults of the multiplexing of the UL-SCH data and the CQI/PMI areg_0˜g_H′−1. In this case, g_i(i=0˜H′−1) is indicative of a column vectorhaving a length (Q_m*N_L). H=(G+N_L*Q_CQI) and H′=H/(N_L*Q_m). N_L isthe number of layers to which an UL-SCH transport block has been mapped.H is a total number of coded bits allocated to the N_L transmissionlayers to which the transport block has been mapped for the UL-SCH dataand CQI/PMI information.

Next, the multiplexed data and CQI/PMI and the separately channel-codedRI and ACK/NACK are subjected to channel interleaving, therebygenerating an output signal at step S99.

Reference Signal (RS)

In a wireless communication system, data is transmitted via a wirelesschannel, and thus, a signal may be distorted during transmission. Inorder for a receiving end to accurately receive, distortion of thereceived signal should be corrected using channel information. In orderto detect channel information, a method of transmitting a signal knownto both a transmitting side and the receiving side and a method ofdetecting channel information using a degree of distortion when a signalis transmitted through a channel are largely used. The afore-mentionedsignal is called a pilot signal or a reference signal (RS).

Also, recently, most mobile communication systems uses a method forenhancing transmission/reception data efficiency by adopting multipletransmit antennas and multiple receive antennas in order to transmit apacket, moving away from the conventional use of a single transmitantenna and a single receive antenna. When data is transmitted orreceived using multiple input/output antennas, a channel state betweenthe transmit antennas and the receive antennas should be detected toaccurately receive a signal. Therefore, each transmit antenna shouldhave a separate reference signal.

In a mobile communication system, an RS may be classified into two typesaccording to its purpose. There are an RS for acquiring channelinformation and an RS used for data demodulation. The former aims atacquiring channel information by a UE to downlink, and thus, the formerRS should be transmitted in a broadband, and even a UE, which does notreceive downlink data in a specific subframe, should receive and measurethe RS. Also, the former RS is used for measurement such as handover, orthe like. The latter RS is an RS transmitted together in a correspondingresource when a base station (BS) transmits it to downlink. Uponreceiving the corresponding RS, the UE may be able to perform channelestimation, and thus, demodulate data. The latter RS should betransmitted in a region in which data is transmitted.

Five types of downlink RS are defined as follows.

-   -   CRS: cell-specific reference signal    -   MBSFN RS: multicast-broadcast single-frequency network reference        signal    -   UE-specific RS or demodulation RS (DM-RS)    -   PRS: positioning reference signal    -   CSI-RS: channel state information reference signal

One RS is transmitted for each downlink antenna port.

The CRS is transmitted in every downlink subframe within a cellsupporting PDSCH transmission. The CRS is transmitted in one or more ofantenna ports 0 to 3. The CRS is defined only in Δf=15 kHz.

The MBSFN RS is transmitted in an MBSFN region of an MBSFN subframe onlywhen a physical multicast channel (PMCH) is transmitted. The MBSFN RS istransmitted in antenna port 4. The MBSFN RS is defined only in anextended CP.

The DM-RS is supported for transmission of a PDSCH and is transmitted inantenna ports p=5, p=7, p=8 or p=7, 8, . . . , ν+6.

Here, u is the number of layers used for transmission of the PDSCH. TheDM-RS is present and valid for PDSCH demodulation only when PDSCHtransmission is associated in a corresponding antenna port. The DM-RS istransmitted only in a resource block (RB) to which the correspondingPDSCH is mapped.

Regardless of the antenna port p, when any one of a physical channel anda physical signal other than the DM-RS is transmitted using an RE of thesame index pair (k,l) in which the DM-RS is transmitted, the DM-RS isnot transmitted in the RE of the corresponding index pair (k,l).

The PRS is transmitted only in a resource block within a downlinksubframe set for PRS transmission.

When both a general subframe and an MBSFN subframe are set aspositioning subframes within one cell, OFDM symbols within the MBSFNsubframe set for PRS transmission use the same CP as that of subframe#0. When only the MBSFN subframe is set as a positioning subframe withinone cell, OMDM symbols set for the PRS within the MBSFN region of thecorresponding subframe use an extended CP.

Within the subframe set for PRS transmission, a starting point of anOFDM symbol set for PRS transmission is the same as a starting point ofa subframe having the same CP length as that of every OFDM symbol setfor the RPS transmission.

The PRS is transmitted in antenna port 6.

The PRS is not mapped to an RE (k,l) allocated to a physical broadcastchannel (PBCH), a PSS, or SSS, regardless of the antenna port p.

The PRS is defined only in Δf=15 kHz.

The CSI-RS is transmitted in 1, 2, 4, or 8 number of antenna ports usingp=15, p=15, 16, p=15, . . . , 18, and p=15, . . . , 22, respectively.

The CSI-RS is defined only in Δf=15 kHz.

The reference signal (RS) will be described in more detail.

The CRS is an RS for obtaining information regarding a state of achannel shared by every terminal within a cell and measuring handover,or the like. The DM-RS is used for data demodulation only for a specificUE. Information for demodulation and channel measurement may be providedusing such reference signals. That is, the DM-RS is used only for datademodulation, and the CRS is used for both purposes of channelinformation obtaining and data demodulation.

The receiving side (i.e., UE) measures a channel state from the CRS, andfeeds back an indicator related to channel quality such as a CQI(Channel Quality Indicator), a PMI (Precoding Matrix Index), a PTI(Precoding Type Indicator) and/or an RI (Rank Indicator) to thetransmitting side (i.e., Base Station). Meanwhile, a reference signalrelated to feedback of channel state information (CSI) may be defined asa CSI-RS.

The DM-RS may be transmitted through resource elements when data on aPDSCH is required to be demodulated. The UE may receive whether a DM-RSis present through a higher layer, and may be valid only when thecorresponding PDSCH is mapped. The DM-RS may be called a UE-specific RSor a demodulation RS (DMRS).

FIG. 10 illustrates a reference signal pattern mapped to a downlinkresource block pair in a wireless communication system to which anembodiment of the present invention may be applied.

Referring to FIG. 10, a downlink resource block pair, that is, a unit inwhich a reference signal is mapped unit, may be represented in the formof one subframe in a time domain×12 subcarriers in a frequency domain.

That is, in a time axis (i.e., x axis), one resource block pair has alength of 14 OFDM symbols in the case of a normal Cyclic Prefix (CP)(FIG. 10(a)) and has a length of 12 OFDM symbols in the case of anextended CP (FIG. 10(b)). In the resource block lattice, ResourceElements (REs) indicated by “0”, “1”, “2”, and “3” mean the positions ofthe CRSs of antenna port indices “0”, “1”, “2”, and “3”, and REsindicated by “D” denotes the position of a DRS.

A CRS is described in detail below. The CRS is used to estimate thechannel of a physical antenna and is a reference signal which may bereceived by all UEs located in a cell in common. The CRS is distributedto the entire frequency bandwidth. Furthermore, the CRS may be used forChannel Quality Information (CQI) and data demodulation.

The CRS is defined in various formats depending on an antenna array onthe transmission side (i.e., an eNB). In a 3GPP LTE system (e.g.,release-8), various antenna arrays are supported, and the transmissionside of a downlink signal has three types of antenna arrays, such as 3single transmission antennas, 2 transmission antennas, and 4transmission antennas. If an eNB uses a single transmission antenna,reference signals for a single antenna port are arrayed. If an eNB uses2 transmission antennas, reference signals for 2 transmission antennaports are arrayed using a Time Division Multiplexing (TDM) method and/ora Frequency Division Multiplexing (FDM) method. That is, different timeresources and/or different frequency resources are allocated so thatreference signals for 2 antenna ports are distinguished from each other.

Furthermore, if an eNB uses 4 transmission antennas, reference signalsfor 4 transmission antenna ports are arrayed using the TDM and/or FDMmethods. Channel information measured by the reception side (i.e., UE)of a downlink signal may be used to demodulate data transmitted using atransmission method, such as single transmission antenna transmission,transmission diversity, closed-loop spatial multiplexing, open-loopspatial multiplexing, or an multi-User-multi-input/output (MIMO)antennas.

If a multi-input/output antenna is supported, when a reference signal istransmitted by a specific antenna port, the reference signal istransmitted in the positions of resource elements specified depending onthe pattern of the reference signal and is not transmitted in thepositions of resource elements specified for other antenna ports. Thatis, reference signals between different antennas do not overlap.

A rule for mapping a CRS to a resource block is defined as follows.

$\begin{matrix}{{k = {{6m} + {( {v + v_{shift}} ){mod}\; 6}}}{l = \{ {{{\begin{matrix}{0,{N_{symb}^{DL} - 3}} & {{{if}\mspace{14mu} p} \in \{ {0,1} \}} \\1 & {{{if}\mspace{14mu} p} \in \{ {2,3} \}}\end{matrix}m} = 0},1,\ldots\mspace{11mu},{{{2 \cdot N_{RB}^{DL}} - {1m^{\prime}}} = {{m + N_{RB}^{\max,{DL}} - {N_{RB}^{DL}v}} = \{ {{\begin{matrix}0 & {{{if}\mspace{14mu} p} = {{0\mspace{14mu}{and}\mspace{14mu} l} = 0}} \\3 & {{{if}\mspace{14mu} p} = {{0\mspace{14mu}{and}\mspace{14mu} l} \neq 0}} \\3 & {{{if}\mspace{14mu} p} = {{1\mspace{14mu}{and}\mspace{14mu} l} = 0}} \\0 & {{{if}\mspace{14mu} p} = {{1\mspace{14mu}{and}\mspace{14mu} l} \neq 0}} \\{3( {n_{s}{mod}\; 2} )} & {{{{if}\mspace{14mu} p} = 2}\mspace{14mu}} \\{3 + {3( {n_{s}{mod}\; 2} )}} & {{{if}\mspace{14mu} p} = 3}\end{matrix}v_{shift}} = {N_{ID}^{cell}{mod}\; 6}} }}} }} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

In Equation 1, k and 1 denote a subcarrier index and a symbol index,respectively, and p denotes an antenna port. N_symb{circumflex over( )}DL denotes the number of OFDM symbols in one downlink slot, andN_RB{circumflex over ( )}DL denotes the number of radio resourcesallocated to downlink. n_s denotes a slot index, and N_ID{circumflexover ( )}cell denotes a cell ID. mod denotes modulo operation. Theposition of a reference signal is different depending on a value v_shiftin a frequency domain. Since the value v_shift depends on a cell ID, theposition of a reference signal has various frequency shift valuesdepending on a cell.

More specifically, in order to improve channel estimation performancethrough a CRS, the position of a CRS may be shifted in a frequencydomain. For example, if reference signals are placed at an interval of 3subcarriers, reference signals in one cell are allocated to a 3k-thsubcarrier, and reference signals in the other cell are allocated to a(3k+1)-th subcarrier. From the point of view of a single antenna port,reference signals are arrayed at an interval of 6 resource elements in afrequency domain. Reference signals are spaced apart from referencesignals allocated in other antenna ports at an interval of 3 resourceelements.

In a time domain, reference signals are started from the symbol index 0of each slot and are arrayed at a constant interval. A time interval isdifferent defined depending on the length of a cyclic prefix. In thecase of a normal cyclic prefix, reference signals are placed in thesymbol indices 0 and 4 of a slot. In the case of an extended cyclicprefix, reference signals are placed in the symbol indices 0 and 3 of aslot. A reference signal for an antenna port that belongs to 2 antennaports and that has a maximum value is defined within one OFDM symbol.Accordingly, in the case of 4 transmission antenna transmission,reference signals for RS antenna ports 0 and 1 are placed in the symbolindices 0 and 4 of a slot (i.e., symbol indices 0 and 3 in the case ofan extended cyclic prefix), and reference signals for antenna ports 2and 3 are placed in the symbol index 1 of the slot. The positions ofreference signals for antenna ports 2 and 3 in a frequency domain arechanged in a second slot.

A DM-RS is described in more detail below. The DM-RS is used todemodulate data. In multi-input/output antenna transmission, precodingweight used for specific UE is combined with a transport channeltransmitted by each transmission antenna when the UE receives areference signal and is used to estimate a corresponding channel withoutany change.

A 3GPP LTE system (e.g., release-8) supports a maximum of 4 transmissionantennas and uses a DM-RS for rank 1 beamforming. The DM-RS for rank 1beamforming also indicates a reference signal for an antenna port index5.

A rule on which a DM-RS is mapped to a resource block is defined asfollows. Equation 13 illustrates a normal cyclic prefix, and Equation 14illustrates an extended cyclic prefix.

$\begin{matrix}{{k = {{( k^{\prime} ){modN}_{sc}^{RB}} + {N_{sc}^{RB} \cdot n_{PRB}}}}{k = \{ {{\begin{matrix}{{4m^{\prime}} + v_{shift}} & {{{if}\mspace{14mu} l} \in \{ {2,3} \}} \\{{4m^{\prime}} + {( {2 + v_{shift}} ){{mod}4}}} & {{{if}\mspace{14mu} l} \in \{ {5,6} \}}\end{matrix}l} = \{ {{\begin{matrix}3 & {l^{\prime} = 0} \\6 & {l^{\prime} = 1} \\2 & {l^{\prime} = 2} \\5 & {l^{\prime} = 3}\end{matrix}l} = \{ {{{\begin{matrix}{0,1} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{2,3} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 1}\end{matrix}m^{\prime}} = 0},1,\ldots\mspace{11mu},{{{3N_{RB}^{PDSCH}} - {1v_{shift}}} = {N_{ID}^{cell}{mod}\; 3}}} } } }} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack \\{{k = {{( k^{\prime} ){modN}_{sc}^{RB}} + {N_{sc}^{RB} \cdot n_{PRB}}}}{k^{\prime} = \{ {{\begin{matrix}{{3m^{\prime}} + v_{shift}} & {{{if}\mspace{14mu} l} = 4} \\{{3m^{\prime}} + {( {2 + v_{shift}} ){mod3}}} & {{{if}\mspace{14mu} l} = 1}\end{matrix}l} = \{ {{\begin{matrix}4 & {l^{\prime} \in \{ {0,2} \}} \\1 & {l^{\prime} = 1}\end{matrix}l^{\prime}} = \{ {{{\begin{matrix}0 & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{1,2} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 1}\end{matrix}m^{\prime}} = 0},1,\ldots\mspace{11mu},{{{4N_{RB}^{PDSCH}} - {1v_{shift}}} = {N_{ID}^{cell}{mod}\; 3}}} } } }} & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$

In Equations 2 and 3, k and 1 denote a subcarrier index and a symbolindex, respectively, and p denotes an antenna port. N_sc{circumflex over( )}RB denotes the size of an RB in a frequency domain and isrepresented as the number of subcarriers. n_PRB denotes the number ofphysical RBs. N_RB{circumflex over ( )}PDSCH denotes the frequencybandwidth of an RB for PDSCH transmission. n_s denotes the index of aslot, and N_ID{circumflex over ( )}cell denotes the ID of a cell. moddenotes modulo operation. The position of a reference signal isdifferent depending on the value v_shift in a frequency domain. Sincethe value v_shift depends on the ID of a cell, the position of areference signal has various frequency shift values depending on a cell.

In Equations 1 to 3, k and p denote a subcarrier index and an antennaport, respectively. N_RB{circumflex over ( )}DL, ns, and N_ID{circumflexover ( )}Cell denote the number of RBs allocated to downlink, the numberof slot indices, and the number of cell IDs. The position of an RS isdifferent depending on the value v_shift from the point of view of afrequency domain.

Sounding Reference Signal (SRS)

An SRS is mostly used in the measurement of channel quality in order toperform uplink frequency-selective scheduling and is not related to thetransmission of uplink data and/or control information, but the presentinvention is not limited thereto. The SRS may be used for various otherpurposes for improving power control or various startup functions of UEswhich have not been recently scheduled. The startup functions mayinclude an initial Modulation and Coding Scheme (MCS), initial powercontrol for data transmission, a timing advance, and frequencysemi-selective scheduling, for example. In this case, the frequencysemi-selective scheduling means selectively allocating a frequencyresource to the first slot of a subframe and pseudo-randomly hopping toanother frequency in the second slot of the subframe and allocatingfrequency resources.

Furthermore, the SRS may be used to measure downlink channel quality,assuming that a radio channel is reciprocal between uplink and downlink.Such an assumption is particularly valid when the same frequencyspectrum is shared between uplink and downlink and in Time DivisionDuplex (TDD) systems separated in a time domain.

The subframes of an SRS transmitted by UE within a cell may berepresented by a cell-specific broadcasting signal. A 4-bitcell-specific parameter “srsSubframeConfiguration” indicates 15available subframe arrays in which an SRS may be transmitted thoughrespective radio frames. In accordance with such arrays, the flexibilityof control of SRS overhead may be provided according to a deploymentscenario.

A sixteenth array completely turns off the switch of an SRS within acell, which is mostly suitable for a serving cell which provides serviceto high-speed UEs.

FIG. 11 illustrates an uplink subframe including the symbols of aSounding Reference Signal (SRS) in a wireless communication system towhich an embodiment of the present invention may be applied.

Referring to FIG. 11, an SRS is always transmitted through the lastSC-FDMA symbol in an arrayed subframe. Accordingly, an SRS and DMRS areplaced in different SC-FDMA symbols.

The transmission of PUSCH data is not permitted in a specific SC-FDMAsymbol for SRS transmission. As a result, if sounding overhead is thehighest, that is, although an SRS symbol is included in all subframes,sounding overhead does not exceed about 7%.

Each SRS symbol is generated based on a base sequence (i.e., a randomsequence or a sequence set based on Zadoff-Ch (ZC)) regarding a giventime unit and frequency bandwidth. All UEs within the same cell use thesame base sequence. In this case, the transmissions of SRSs from aplurality of UEs within the same cell in the same frequency bandwidthand the same time are orthogonal to each other by different cyclicshifts of a base sequence and are distinguished from each other.

SRS sequences from different cells may be distinguished from each otherbecause different base sequences are allocated to respective cells, butorthogonality between the different base sequences is not guaranteed.

General Carrier Aggregation

A communication environment taken into consideration in embodiments ofthe present invention includes a multi-carrier support environment. Thatis, a multi-carrier system or Carrier Aggregation (CA) system that isused in an embodiment of the present invention refers to a system inwhich one or more Component Carriers (CCs) having a smaller bandwidththan a target bandwidth are aggregated and used when the target widebandis configured in order to support a wideband.

In an embodiment of the present invention, a multi-carrier means of anaggregation of carriers (or a carrier aggregation). In this case, anaggregation of carriers means both an aggregation between contiguouscarriers and an aggregation between discontiguous (or non-contiguous)carriers. Furthermore, the number of CCs aggregated between downlink anduplink may be different. A case where the number of downlink CCs(hereinafter called “DL CCs”) and the number of uplink CCs (hereinaftercalled “UL CCs”) are the same is called a symmetric aggregation. A casewhere the number of DL CCs is different from the number of UL CCs iscalled an asymmetric aggregation. Such the term of a carrier aggregationmay be replaced with terms, such as a carrier aggregation, bandwidthaggregation, or spectrum aggregation.

An object of a carrier aggregation configured by aggregating two or morecomponent carriers is to support up to a 100 MHz bandwidth in an LTE-Asystem. When one or more carriers having a smaller bandwidth than atarget bandwidth are aggregated, the bandwidth of the aggregatedcarriers may be restricted to a bandwidth which is used in an existingsystem in order to maintain backward compatibility with an existing IMTsystem. For example, in an existing 3GPP LTE system, {1.4, 3, 5, 10, 15,20} MHz bandwidths may be supported. In a 3GPP LTE-advanced system(i.e., LTE-A), bandwidths greater than the bandwidth 20 MHz may besupported using only the bandwidths for a backward compatibility withexisting systems. Furthermore, in a carrier aggregation system used inan embodiment of the present invention, new bandwidths may be definedregardless of the bandwidths used in the existing systems in order tosupport a carrier aggregation.

An LTE-A system uses the concept of a cell in order to manage radioresources.

The aforementioned carrier aggregation environment may also be called amulti-cell environment. A cell is defined as a combination of a pair ofa downlink resource (DL CC) and an uplink resource (UL CC), but anuplink resource is not an essential element. Accordingly, a cell mayconsist of a downlink resource only or a downlink resource and an uplinkresource. If specific UE has a single configured serving cell, it mayhave 1 DL CC and 1 UL CC. If specific UE has two or more configuredserving cells, it has DL CCs corresponding to the number of cells, andthe number of UL CCs may be the same as or smaller than the number of DLCCs.

In some embodiments, a DL CC and an UL CC may be configured in anopposite way. That is, if specific UE has a plurality of configuredserving cells, a carrier aggregation environment in which the number ofUL CCs is greater than the number of DL CCs may also be supported. Thatis, a carrier aggregation may be understood as being an aggregation oftwo or more cells having different carrier frequency (the centerfrequency of a cell). In this case, the “cell” should be distinguishedfrom a “cell”, that is, a region commonly covered by an eNB.

A cell used in an LTE-A system includes a Primary Cell (PCell) and aSecondary Cell (SCell). A PCell and an SCell may be used as servingcells. In the case of UE which is in an RRC_CONNECTED state, but inwhich a carrier aggregation has not been configured or which does notsupport a carrier aggregation, only one serving cell configured as onlya PCell is present. In contrast, in the case of UE which is in theRRC_CONNECTED state and in which a carrier aggregation has beenconfigured, one or more serving cells may be present. A PCell and one ormore SCells are included in each serving cell.

A serving cell (PCell and SCell) may be configured through an RRCparameter. PhysCellId is the physical layer identifier of a cell and hasan integer value from 0 to 503. SCellIndex is a short identifier whichis used to identify an SCell and has an integer value of 1 to 7.ServCellIndex is a short identifier which is used to identify a servingcell (PCell or SCell) and has an integer value of 0 to 7. The value 0 isapplied to a PCell, and SCellIndex is previously assigned in order toapply it to an SCell. That is, in ServCellIndex, a cell having thesmallest cell ID (or cell index) becomes a PCell.

A PCell means a cell operating on a primary frequency (or primary CC). APCell may be used for UE to perform an initial connection establishmentprocess or a connection re-establishment process and may refer to a cellindicated in a handover process. Furthermore, a PCell means a cell thatbelongs to serving cells configured in a carrier aggregation environmentand that becomes the center of control-related communication. That is,UE may receive a PUCCH allocated only in its PCell and send the PUCCHand may use only the PCell to obtain system information or to change amonitoring procedure. An Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN) may change only a PCell for a handover procedure usingthe RRC connection reconfiguration (RRCConnectionReconfiguration)message of a higher layer including mobility control information(mobilityControlInfo) for UE which supports a carrier aggregationenvironment.

An SCell may mean a cell operating on a secondary frequency (orsecondary CC). Only one PCell is allocated to specific UE, and one ormore SCells may be allocated to the specific UE. An SCell may beconfigured after RRC connection is established and may be used toprovide additional radio resources. A PUCCH is not present in theremaining cells, that is, SCells that belong to serving cells configuredin a carrier aggregation environment and that do not include a PCell.When adding an SCell to UE supporting a carrier aggregation environment,an E-UTRAN may provide all types of system information related to theoperation of a related cell in the RRC_CONNECTED state through adedicated signal. A change of system information may be controlled byreleasing and adding a related SCell. In this case, the RRC connectionreconfiguration (RRCConnectionReconfiguration) message of a higher layermay be used. An E-UTRAN may send dedicated signaling having a differentparameter for each UE instead of broadcasting within a related SCell.

After an initial security activation process is started, an E-UTRAN mayconfigure a network including one or more SCells by adding to a PCellthat is initially configured in a connection establishing process. In acarrier aggregation environment, a PCell and an SCell may operaterespective component carriers. In the following embodiments, a PrimaryComponent Carrier (PCC) may be used as the same meaning as a PCell, anda Secondary Component Carrier (SCC) may be used as the same meaning asan SCell.

FIG. 12 shows an example of component carriers and carrier aggregationin a wireless communication system to which an embodiment of the presentinvention may be applied.

(a) of FIG. 12 illustrates a single carrier structure used in an LTEsystem. Component carriers include a DL CC and a UL CC. One CC may havea frequency range of 20 MHz.

(b) of FIG. 12 illustrates a carrier aggregation structure used in anLTE_A system. (b) of FIG. 12 illustrates a case in which three CCshaving a frequency size of 20 MHz are combined. Three DL CCs and threeUL CCs are provided, but there is no limitation in the number of DL CCsand UL CCs. In the case of carrier aggregation, the UE maysimultaneously monitor three CCs, receive downlink signal/data, andtransmit uplink signal/data.

If N DL CCs are managed in a specific cell, a network may allocate M(M≤N) DL CCs to UE. In this case, the UE may monitor only the M limitedDL CCs and receive a DL signal. Furthermore, a network may give priorityto L (L≤M≤N) DL CCs and allocate major DL CCs to UE. In this case, theUE must monitor the L DL CCs. Such a method may be applied to uplinktransmission in the same manner.

A linkage between a carrier frequency (or DL CC) of a downlink resourceand a carrier frequency (or UL CC) of an uplink resource may beindicated by a higher layer message, such as an RRC message, or systeminformation. For example, a combination of DL resources and UL resourcesmay be configured by a linkage defined by System Information Block Type2 (SIB2). Specifically, the linkage may mean a mapping relationshipbetween a DL CC in which a PDCCH carrying an UL grant is transmitted andan UL CC in which the UL grant is used and may mean a mappingrelationship between a DL CC (or UL CC) in which data for an HARQ istransmitted and an UL CC (or DL CC) in which an HARQ ACK/NACK signal istransmitted.

Cross-Carrier Scheduling

In a carrier aggregation system, there are two methods, that is, aself-scheduling method and a cross-carrier scheduling method form thepoint of view of scheduling for a carrier or a serving cell.Cross-carrier scheduling may also be called cross-component carrierscheduling or cross-cell scheduling.

Cross-carrier scheduling means that a PDCCH (DL grant) and a PDSCH aretransmitted in different DL CCs or that a PUSCH transmitted according toa PDCCH (UL grant) transmitted in a DL CC is transmitted through an ULCC different from an UL CC that is linked to the DL CC through which theUL grant has been received.

Whether cross-carrier scheduling will be performed may be activated ordeactivate in a UE-specific way, and each UE may be notified throughhigh layer signaling (e.g., RRC signaling) semi-statically.

If cross-carrier scheduling is activated, there is a need for a CarrierIndicator Field (CIF) providing notification that a PDSCH/PUSCHindicated by a PDCCH is transmitted through which D/UL CC. For example,a PDCCH may allocate a PDSCH resource or PUSCH resource to any one of aplurality of component carriers using a CIF. That is, if a PDCCH on a DLCC allocates a PDSCH or PUSCH resource to one of multi-aggregated DL/ULCCs, a CIF is configured. In this case, a DCI format of LTE-A Release-8may be extended according to the CIF. In this case, the configured CIFmay be fixed to a 3-bit field, and the position of the configured CIFmay be fixed regardless of the size of the DCI format. Furthermore, aPDCCH structure (resource mapping based on the same coding and the sameCCE) of LTE-A Release-8 may be reused.

In contrast, if a PDCCH on a DL CC allocates a PDSCH resource on thesame DL CC or allocates a PUSCH resource on a single-linked UL CC, a CIFis not configured. In this case, the same PDCCH structure (resourcemapping based on the same coding and the same CCE) and DCI format asthose of LTE-A Release-8 may be used.

If cross-carrier scheduling is possible, UE needs to monitor a PDCCH fora plurality of pieces of DCI in the control region of a monitoring CCbased on a transmission mode and/or bandwidth corresponding to each CC.Accordingly, there is a need for the configuration of a search space andPDCCH monitoring capable of supporting such monitoring.

In a carrier aggregation system, a UE DL CC set is indicative of a setof DL CCs scheduled so that UE receives a PDSCH. A UE UL CC set isindicative of a set of UL CCs scheduled so that UE transmits a PUSCH.Furthermore, a PDCCH monitoring set is indicative of a set of one ormore DL CCs for performing PDCCH monitoring. A PDCCH monitoring set maybe the same as a UE DL CC set or may be a subset of a UE DL CC set. APDCCH monitoring set may include at least one of DL CCs within a UE DLCC set. Alternatively, a PDCCH monitoring set may be separately definedregardless of a UE DL CC set. DL CCs included in a PDCCH monitoring setmay be configured so that self-scheduling for a linked UL CC is alwayspossible. Such a UE DL CC set, UE UL CC set, and PDCCH monitoring setmay be configured in a UE-specifically, UE group-specifically, orcell-specifically.

If cross-carrier scheduling is deactivated, it means that a PDCCHmonitoring set is always the same as UE DL CC set. In this case, thereis no indication, such as separate signaling for a PDCCH monitoring set.However, if cross-carrier scheduling is activated, a PDCCH monitoringset may be defined in a UE DL CC set. That is, in order to schedule aPDSCH or PUSCH for UE, an eNB transmits a PDCCH through a PDCCHmonitoring set only.

FIG. 13 shows an example of a structure of a subframe according tocross-carrier scheduling in a wireless communication system to which anembodiment of the present invention may be applied.

Referring to FIG. 13, in a DL subframe for an LTE-A UE, three DL CCs arecombined and DL CC ‘A’ indicates a case set with a PDCCH monitoring DLCC. In case where a CIF is not used, each DL CC may transmit a PDCCHscheduling a PDSCH thereof without a CIF. Meanwhile, in case where theCIF is used through higher layer signaling, only one DL CC ‘A’ maytransmit the PDCCH scheduling a PDSCH thereof or a PDSCH of another CCusing the CIF. Here, DL CC ‘B’ and ‘C’ not set as PDCCH monitoring DLCCs do not transmit the PDCCH.

PDCCH Transmission

The eNB determines a PDCCH format according to a DCI to be transmittedto the UE, and attaches a CRC (Cyclic Redundancy Check) to controlinformation. A unique identifier (which is called an RNTI (Radio NetworkTemporary Identifier)) is masked to the CRC according to an owner of thePDCCH or a purpose thereof. In the case of a PDCCH for a specific UE, aunique identifier of a UE, e.g., a C-RNTI (Cell-RNTI), may be masked tothe CRC. Or, in the case of a PDCCH for a paging message, a pagingindication identifier, e.g., a P-RNTI (Paging-RNTI) may be masked to theCRC. In the case of a PDCCH for system information, specifically, asystem information block (SIB), a system information identifier or anSI-RNTI (system information RNTI) may be masked to the CRC. In order toindicate a random access response, a response with respect totransmission of a random access preamble of a UE, an RA-RNTI (randomaccess-RNTI) may be masked to the CRC.

Thereafter, the BS performs channel coding on CRC-added controlinformation to generate coded data. Here, the BS may perform channelcoding at a code rate according to an MCS level. The BS may perform ratematching according to a CCE aggregation level allocated to a PDCCHformat, and modulates the coded data to generate modulated symbols.Here, a modulation order according to the MCS level may be used. A CCEaggregation level of modulated symbols forming one PDCCH may be one of1, 2, 4 and 8. Thereafter, the BS maps the modulated symbols to physicalresource elements (CCE to RE mapping).

A plurality of PDCCHs may be transmitted in one subframe. That is, acontrol region of one subframe includes a plurality of CCEs having anindex 0˜N_(CCE,k)−1. Here, N(CCE, k) denotes a total number of CCE swithin a control region of a kth subframe. The UE monitors a pluralityof PDCCHs in each subframe.

Here, monitoring refers to UE attempting to decode PDCCHs according to amonitored PDCCH format. In a control region allocated within a subframe,the BS does not provide information regarding where a correspondingPDCCH is present. In order to receive a control channel transmitted fromthe BS, the UE searches for a PDCCH thereof by monitoring an aggregationof PDCCH candidates within a subframe because the UE does not know inwhich position, at which CCE aggregation level, or in which DCI format,the PDCCH thereof is transmitted. This is called blinddecoding/detection (BD). Blind decoding refers to a method by which theUE de-masks a UE ID thereof in a CRC portion and checks a CRC error todetermine whether a corresponding PDCCH is a control channel of the UE.

In the active mode, the UE monitors a PDCCH of each subframe to receivedata transmitted to the UE. In a DRX mode, the UE wakes up in amonitoring section of each DRX period to monitor a PDCCH in a subframecorresponding to a monitoring section. A subframe in which PDCCH ismonitored is called a non-DRX subframe.

In order to receive the PDCCH transmitted to the UE, the UE shouldperform blind decoding on all CCEs present in the control region of thenon-DRX subframe. Since the UE does not know which PDCCH format will betransmitted, the UE should decode all PDCCHs at a possible CCEaggregation level until the blind decoding of the PDCCH is successful inevery non-DRX subframe. Since the UE does not know how many CCEs thePDCCH for itself uses, the UE should attempt detection at all possibleCCE aggregation levels until the blind decoding of the PDCCH issuccessful. That is, the UE performs blind decoding by each CCEaggregation level. That is, the UE first attempts at decoding at a CCEaggregation level unit by 1. If decoding fails, the UE attempts atdecoding at the CCE aggregate level unit by 2. Thereafter, the UEattempts at decoding the CCE aggregation level unit by 4 and the CCEaggregation level unit by 8 again. Also, the UE attempts at blinddecoding on all four C-RNTI, P-RNTI, SI-RNTI and RA-RNTI. In addition,the UE attempts at blind decoding on all DCI formats to be monitored.

In this manner, if the UE attempts at blind decoding by every CCEaggregation level for all DCI formats to be monitored for all possibleRNTIs, the number of detection attempts will be excessively increase,and thus, in the LTE system, a search space (SS) concept is defined forblind decoding of the UE. Search space refers to a PDCCH candidate setfor monitoring, and may have a different size according to each PDCCHformat.

The search space may include a common search space (CSS) and aUE-specific/dedicated search space (USS). In the case of the commonsearch space, all terminals may know a size of the common search space,but the UE-specific search space may be set individually for eachterminal. Accordingly, the UE should monitor both the UE-specific searchspace and the common search space in order to decode the PDCCH, andthus, the UE performs blind decoding (BD) at a maximum of 44 times inone sub-frame. Here, blind decoding performed in accordance withdifferent CRC values (e.g., C-RNTI, P-RNTI, SI-RNTI, RA-RNTI) is notincluded.

Due to the small search space, it may happen that eNB fails to securethe CCE resources for transmitting the PDCCH to all the UEs to which thePDCCH is to be transmitted within a given subframe. This is becauseresources remaining after the CCE location are allocated may not beincluded in the search space of the specific UE. In order to minimizesuch barriers that may continue in a next sub-frame, a UE-specifichopping sequence may be applied to a starting point of the UE-specificsearch space.

Table 4 shows a size of the common search space, and a size of theUE-specific search space.

TABLE 4 Number PDCCH of CCEs Number of candidates Number of candidatesformat (n) in common search space in dedicated search space 0 1 — 6 1 2— 6 2 4 4 2 3 8 2 2

In order to alleviate the computational load of the UE according to thenumber of attempts at blind decoding, the UE does not simultaneouslyperform search according to all defined DCI formats. In detail, the UEmay always perform search for DCI format 0 and 1A in the UE-specificsearch space. At this time, DCI formats 0 and 1A have the same size, butthe UE may differentiate between the DCI format using a flag (for format0/format 1A differentiation) used for differentiating between DCIformats 0 and 1A included in the PDCCH. Also, according to the PDSCHtransmission mode set by the eNB, a DCI format other than the DCIformats 0 and 1A may be required for the terminal. For example, thereare DCI formats 1, 1B, and 2.

In the common search space, the UE may search the DCI formats 1A and 1C.Also, the UE may be configured to search for DCI format 3 or 3A, and DCIformats 3 and 3A have the same size as DCI formats 0 and 1A, but the UEmay differentiate the DCI formats using the CRC scrambled by anidentifier other than a UE-specific identifier.

A search space S_k{circumflex over ( )}(L) refers to a PDCCH candidateset according to an aggregation level L∈{1,2,4,8}. A CCE according to aPDCCH candidate set m of a search space may be determined by Equation 4below.L·{(Y _(k) +m)mod └N _(CCE,k) /L┘}+i  [Equation 4]

Here, M_(L) denotes the number of PDCCH candidates according to a CCEaggregation level L for monitoring, and m=0˜M{circumflex over ( )}(L)−1.i denotes an index designating an individual CCE in each PDCCHcandidate, and i=0˜L−1.

As described above, the UE monitors both the UE-specific search spaceand the common search space to decode the PDCCH. Here, the common searchspace (CSS) supports PDCCHs having an aggregation level {4, 8}, and theUE-specific search space (USS) supports PDCCHs having an aggregationlevel {1, 2, 4, 8}

Table 5 shows PDCCH candidates monitored by the UE.

TABLE 5 Search space S_(k) ^((L)) Number of PDCCH Type Aggregation levelL Size [in CCEs] candidates M^((L)) UE- 1 6 6 specific 2 12 6 4 8 2 8 162 Common 4 16 4 8 16 2

Referring to Equation 4, in the case of the CSS, Y_(k) is set to 0 fortwo aggregation levels L=4 and L=8. Meanwhile, in the case of theUE-specific SS (USS), Y_(k) is defined as expressed by Equation 5 for anaggregation level L.Y _(k)=(A·Y _(k-1))mod D  [Equation 5]

Here, Y⁻¹=n_(RNTI)≠0, and an RNTI value used for n_(RNTI) may be definedas one of identifiers of the UE. Also, A=39827, D=65537, andk=└n_(s)/2┘. Here, n_s denotes a slot number (or index) in a radioframe.

General ACK/NACK Multiplexing Method

In a situation in which UE has to simultaneously send a plurality ofACK/NACKs corresponding to a plurality of data units received from aneNB, an ACK/NACK multiplexing method based on the selection of a PUCCHresource may be taken into consideration in order to maintain the singlefrequency characteristic of an ACK/NACK signal and to reduce ACK/NACKtransmission power.

The content of ACK/NACK responses for a plurality of data units,together with ACK/NACK multiplexing, is identified by a combination of aPUCCH resource used in actual ACK/NACK transmission and the resource ofQPSK modulation symbols.

For example, if one PUCCH resource sends 4 bits and a maximum of 4 dataunits are transmitted, ACK/NACK results may be identified in an eNB asin Table 6 below.

TABLE 6 HARQ-ACK(0), HARQ-ACK(1), HARQ-ACK(2), b(0), HARQ-ACK(3)n_(PUCCH) ⁽¹⁾ b(1) ACK, ACK, ACK, ACK n_(PUCCH,1) ⁽¹⁾ 1, 1 ACK, ACK,ACK, NACK/DTX n_(PUCCH,1) ⁽¹⁾ 1, 0 NACK/DTX, NACK/DTX, NACK, DTXn_(PUCCH,2) ⁽¹⁾ 1, 1 ACK, ACK, NACK/DTX, ACK n_(PUCCH,1) ⁽¹⁾ 1, 0 NACK,DTX, DTX, DTX n_(PUCCH,0) ⁽¹⁾ 1, 0 ACK, ACK, NACK/DTX, NACK/DTXn_(PUCCH,1) ⁽¹⁾ 1, 0 ACK, NACK/DTX, ACK, ACK n_(PUCCH,3) ⁽¹⁾ 0, 1NACK/DTX, NACK/DTX, NACK/DTX, NACK n_(PUCCH,3) ⁽¹⁾ 1, 1 ACK, NACK/DTX,ACK, NACK/DTX n_(PUCCH,2) ⁽¹⁾ 0, 1 ACK, NACK/DTX, NACK/DTX, ACKn_(PUCCH,0) ⁽¹⁾ 0, 1 ACK, NACK/DTX, NACK/DTX, NACK/DTX n_(PUCCH,0) ⁽¹⁾1, 1 NACK/DTX, ACK, ACK, ACK n_(PUCCH,3) ⁽¹⁾ 0, 1 NACK/DTX, NACK, DTX,DTX n_(PUCCH,1) ⁽¹⁾ 0, 0 NACK/DTX, ACK, ACK, NACK/DTX n_(PUCCH,2) ⁽¹⁾ 1,0 NACK/DTX, ACK, NACK/DTX, ACK n_(PUCCH,3) ⁽¹⁾ 1, 0 NACK/DTX, ACK,NACK/DTX, NACK/DTX n_(PUCCH,1) ⁽¹⁾ 0, 1 NACK/DTX, NACK/DTX, ACK, ACKn_(PUCCH,3) ⁽¹⁾ 0, 1 NACK/DTX, NACK/DTX, ACK, NACK/DTX n_(PUCCH,2) ⁽¹⁾0, 0 NACK/DTX, NACK/DTX, NACK/DTX, ACK n_(PUCCH,3) ⁽¹⁾ 0, 0 DTX, DTX,DTX, DTX N/A N/A

In Table 6, HARQ-ACK(i) indicates an ACK/NACK result regarding ith dataunit. In Table 3, DTX (DTX (Discontinuous Transmission) refers to thatthere is no data unit to be transmitted for the correspondingHARQ-ACK(i) or the UE cannot detect a data unit corresponding to theHARQ-ACK(i).

According to Table 6, there are a maximum of four PUCCH resources, andb(0) and b(1) are two bits transmitted using a selected PUCCH.

For example, when the UE successfully receives four data units, the UEtransmits 2-bit (1,1) using n_(PUCCH, 1) {circumflex over ( )}(1).

When the UE is unsuccessful in decoding in first and third data unitsand successful in decoding in second and fourth data units, the UEtransmits a bit (1,0) using n_(PUCCH, 1) {circumflex over ( )}(3).

In ACK/NACK channel selection, when at least one ACK is present, NACKand DTX are coupled. This is because a combination of a reserved PUCCHresource and QPSK symbol cannot indicate every ACK/NACK state. However,without ACK, DTX is decoupled from the NACK.

In this case, a PUCCH resource linked to a data unit corresponding toone definite NACK may also be reserved for transmitting a signal of aplurality of ACK/NACKs.

Block Spreading Technique

The block spreading technique is a scheme that modulates transmission ofthe control signal by using the SC-FDMA scheme unlike the existing PUCCHformat 1 series or 2 series. As illustrated in FIG. 14, a symbolsequence may be spread and transmitted on the time domain by using anorthogonal cover code (OCC). The control signals of the plurality ofterminals may be multiplexed on the same RB by using the OCC. In thecase of PUCCH format 2 described above, one symbol sequence istransmitted throughout the time domain and the control signals of theplurality of terminals are multiplexed by using the cyclic shift (CS) ofthe CAZAC sequence, while in the case of a block spreading based onPUCCH format (for example, PUCCH format 3), one symbol sequence istransmitted throughout the frequency domain and the control signals ofthe plurality of terminals are multiplexed by using the time domainspreading using the OCC.

FIG. 14 illustrates one example of generating and transmitting 5 SC-FDMAsymbols during one slot in the wireless communication system to whichthe present invention may be applied.

In FIG. 14, an example of generating and transmitting 5 SC-FDMA symbols(that is, data part) by using an OCC having the length of 5(alternatively, SF=5) in one symbol sequence during one slot. In thiscase, two RS symbols may be used during one slot.

In the example of FIG. 14, the RS symbol may be generated from a CAZACsequence to which a specific cyclic shift value is applied andtransmitted in a type in which a predetermined OCC is applied(alternatively, multiplied) throughout a plurality of RS symbols.Further, in the example of FIG. 8, when it is assumed that 12 modulatedsymbols are used for each OFDM symbol (alternatively, SC-FDMA symbol)and the respective modulated symbols are generated by QPSK, the maximumbit number which may be transmitted in one slot becomes 24 bits (=12×2).Accordingly, the bit number which is transmittable by two slots becomesa total of 48 bits. When a PUCCH channel structure of the blockspreading scheme is used, control information having an extended sizemay be transmitted as compared with the existing PUCCH format 1 seriesand 2 series.

Hybrid—Automatic Repeat and Request (HARQ)

In a mobile communication system, one eNB sends and receives data to andfrom a plurality of UEs in one cell/sector through a wireless channelenvironment.

In a system in which multiple carriers operate or a system operating ina form similar to the system, an eNB receives packet traffic over awired Internet and sends the received packet traffic to UE using apredetermined communication method. In this case, it is a downlinkscheduling that the eNB determines to send data to which UE using whichfrequency domain at which timing.

Furthermore, the eNB receives data from the UE using a predeterminedcommunication method, demodulates the received data, and sends packettraffic through the wired Internet. It is an Uplink scheduling that theeNB determines to allow which UE to send uplink data using whichfrequency band at which timing. In general, UE having a better channelstate sends and receives data using more time and more frequencyresources.

FIG. 15 is a diagram illustrating a time-frequency resource block in atime frequency domain in a wireless communication system to which anembodiment of the present invention may be applied.

Resources in a system in which multiple carriers operate and a systemoperating in a form similar to the system may be basically divided intoa time domain and a frequency domain. The resources may be defined asresource blocks. The resource block includes specific N subcarriers andspecific M subframes or a predetermined time unit. In this case, N and Mmay be 1.

In FIG. 15, one square means one resource block, and one resource blockuse several subcarriers as one axis and a predetermined time unit as theother axis. In downlink, an eNB schedules one or more resource blocksfor selected UE according to a predetermined scheduling rule, and sendsdata to the UE using allocated resource blocks. In uplink, an eNBschedules one or more resource blocks to selected UE according to apredetermined scheduling rule, and the UE sends data using the allocatedresource in uplink.

After the scheduling and the data is transmitted, an error controlmethod if a frame is lost or damaged includes an automatic repeatrequest (ARQ) method and a hybrid ARQ (HARQ) method of a more advancedform.

Basically, in the ARQ method, after one frame is transmitted, atransmission side waits for an acknowledgement message (ACK). Areception side sends an acknowledgement message (ACK) only when theframe is successfully received. If an error is generated in the receivedframe, the reception side sends a negative-ACK (NACK) message again anddeletes information about the received frame having an error from areception end buffer. When an ACK signal is received, a transmissionside sends a subsequent frame. When a NACK message is received, thetransmission side resends a corresponding frame.

Unlike in the ARQ method, in the HARQ method, if a received frame cannotbe demodulated, a reception end sends a NACK message to a transmissionend, but stores an already received frame in a buffer during a specifictime and combines the stored frame with a previously received from whenthe corresponding frame is retransmitted, thereby increasing a successrate of reception.

Recently, the HARQ method more efficient than the basic ARQ method iswidely used. Such an HARQ method includes several types. The HARQ methodmay be basically divided into synchronous HARQ and asynchronous HARQdepending on retransmission timing and may be divided into achannel-adaptive method and a channel-non-adaptive method depending onwhether a channel state is incorporated into the amount of resourcesused upon retransmission.

In the synchronous HARQ method, when initial transmission fails,subsequent retransmission is performed by a system according topredetermined timing. That is, assuming that timing upon retransmissionis performed every fourth time unit after an initial transmissionfailure, an eNB and UE do not need to be additionally notified of suchtiming because the timing has already been agreed between the eNB andthe UE. In this case, if a data transmission side has received an NACKmessage, it retransmits a frame every fourth time unit until it receivesan ACK message.

In contrast, in the asynchronous HARQ method, retransmission timing maybe newly scheduled or may be performed through additional signaling.Timing when retransmission for a previously failed frame is performed ischanged depending on several factors, such as a channel state.

In the channel-non-adaptive HARQ method, the modulation of a frame uponretransmission, the number of resource blocks, and adaptive modulationand coding (AMC) are performed as they have been predetermined uponinitial transmission. In contrast, in the channel-adaptive HARQ method,the modulation of a frame upon retransmission, the number of resourceblocks, and adaptive modulation and coding (AMC) are performed arechanged depending on the state of a channel. For example, in thechannel-non-adaptive HARQ method, a transmission side sends data using 6resource blocks upon initial transmission and performs retransmissionusing 6 resource blocks upon subsequent retransmission in the samemanner. In contrast, in the channel-adaptive HARQ method, althoughtransmission has been performed using 6 resource blocks, retransmissionis subsequently performed using resource blocks greater than or smallerthan the 6 resources blocks depending on a channel state.

Four HARQ combinations may be performed based on such a classification,but a HARQ method that are used primarily includes an asynchronous andchannel-adaptive HARQ method and a synchronous and channel-non-adaptiveHARQ method.

The asynchronous and channel-adaptive HARQ method may maximizeretransmission efficiency because retransmission timing and the amountof resources used are adaptively changed depending on the state of achannel, but has a disadvantage in that overhead is increased.Accordingly, the asynchronous and channel-adaptive HARQ method is nottaken into consideration in common for uplink.

The synchronous and channel-non-adaptive HARQ method is advantageous inthat overhead for timing for retransmission and resource allocation israrely present because the timing for retransmission and the resourceallocation have been predetermined within a system, but isdisadvantageous in that retransmission efficiency is very low if such amethod is used in a channel state that varies severely.

FIG. 16 is a diagram illustrating a resource allocation andretransmission process of the asynchronous HARQ method in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

For example, in the case of downlink, after scheduling is performed anddata is transmitted, ACK/NACK information is received from UE. Timedelay is generated until next data is transmitted as shown in FIG. 16.The time delay is generated due to channel propagation delay and thetime taken for data decoding and data encoding.

For such a delay period, a method for sending data using an independentHARQ process is used for blankless data transmission. For example, ifthe shortest cycle between next data transmission and subsequent datatransmission is 7 subframes, data may be transmitted without a blank if7 independent processes are placed in the 7 subframes.

An LTE physical layer supports HARQ in a PDSCH and a PUSCH andassociated reception acknowledge (ACK) feedback in a separate controlchannel is transmitted.

In an LTE FDD system, if the LTE FDD system does not operate in MIMO, 8stop-and-wait (SAW) HARQ processes are supported in uplink and downlinkboth in a constant round trip time (RTT) of 8 ms.

CA-Based CoMP Operation

In system subsequent to LTE, cooperative multi-point (CoMP) transmissionmay be implemented using a carrier aggregation (CA) function in LTE.

FIG. 17 is a diagram illustrating a carrier aggregation-based CoMPsystem in a wireless communication system to which an embodiment of thepresent invention may be applied.

FIG. 17 illustrates that a primary cell (PCell) carrier and a secondarycell (SCell) carrier use the same frequency band on a frequency axis andare respectively allocated to two eNBs that are geographically spacedapart from each other.

A serving eNB allocates a PCell to UE1, and an neighboring eNB providingmuch interference allocates an SCell, so that Various DL/UL CoMPoperations such as JT, CS/CB, and dynamic cell selection may beperformed.

FIG. 17 shows an example in which UE aggregates two eNBs as a PCell andan SCell, respectively. Practically, UE may aggregate three or morecells, and a CoMP operation on some of the three cells in the samefrequency band may be performed and a simple CA operation on other cellsin a different frequency band may be performed. In this case, the PCelldoes not need to take part in the CoMP operation.

UE Procedure for Receiving PDSCH

When UE detects a PDCCH of a serving cell on which a DCI format 1, 1A,1B, 1C, 1D, 2, 2A, 2B or 2C intended for the UE is carried other than asubframe(s) indicated by a higher layer parameter“mbsfn-SubframeConfigList”, the UE decodes a corresponding PDSCH in thesame subframe with the restriction of the number of transport blocksdefined in a higher layer.

UE decodes a PDSCH according to a detected PDCCH with CRC scrambled byan SI-RNTI or P-RNTI on which a DCI format 1A, 1C intended for the UE iscarried, and assumes that a PRS is not present in a resource block (RB)on which the corresponding PDSCH is carried.

UE in which a carrier indicator field (CIF) for a serving cell isconfigured assumes that a CIF is not present in any PDCCH of a servingcell within a common search space.

Otherwise, when PDCCH CRC is scrambled by a C-RNTI or an SPS C-RNTI, UEin which a CIF is configured assumes that a CIF for a serving cell ispresent in a PDCCH that is located within a UE-specific search space.

When UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by an SI-RNTI, the UE decodes the PDCCH and acorresponding PDSCH according to a combination defined in Table 3 below.The PDSCH corresponding to the PDCCH(s) is scrambling-initialized by theSI-RNTI.

Table 7 illustrates a PDCCH and PDSCH configured by an SI-RNTI.

TABLE 7 DCI SEARCH METHOD FOR SENDING PDSCH FORMAT SPACE CORRESPONDINGTO PDCCH DCI format common If the number of PBCH antenna ports is 1, 1Ca single antenna port, a port 0 is used, and if not, transmit diversityDCI format common If the number of PBCH antenna ports is 1, a 1A singleantenna port, a port 0 is used, and if not, transmit diversity

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by a P-RNTI, the UE decodes the PDCCH and a correspondingPDSCH according to a combination defined in Table 4 below. The PDSCHcorresponding to the PDCCH(s) is scrambling-initialized by the P-RNTI.

Table 8 illustrates a PDCCH and PDSCH configured by a P-RNTI.

TABLE 8 DCI SEARCH METHOD FOR SENDING PDSCH FORMAT SPACE CORRESPONDINGTO PDCCH DCI format common If the number of PBCH antenna ports is 1, a1C single antenna port, a port 0 is used, and if not, transmit diversityDCI format common If the number of PBCH antenna ports is 1, a 1A singleantenna port, a port 0 is used, and if not, transmit diversity

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by an RA-RNTI, the UE decodes the PDCCH and acorresponding PDSCH according to a combination defined in Table 5 below.The PDSCH corresponding to the PDCCH(s) is scrambling-initialized by theRA-RNTI.

Table 9 illustrates a PDCCH and PDSCH configured by an RA-RNTI.

TABLE 9 SEARCH METHOD FOR SENDING PDSCH DCI FORMAT SPACE CORRESPONDINGTO PDCCH DCI format 1C common If the number of PBCH antenna ports is 1,a single antenna port, a port 0 is used, and if not, transmit diversityDCI format 1A common If the number of PBCH antenna ports is 1, a singleantenna port, a port 0 is used, and if not, transmit diversity

UE may be semi-statically configured through higher layer signaling sothat it receives PDSCH data transmission signaled through a PDCCH inaccordance with any one of 9 transmission modes, including a mode 1 to amode 9.

In the case of the frame structure type 1,

-   -   UE does not receive a PDSCH RB transmitted in the antenna port 5        even in any subframe in which the number of OFDM symbols for a        PDCCH having a common CP is 4.    -   If any one of 2 physical resource blocks (PRBs) to which a        virtual resource block (VRB) pair is mapped overlaps a frequency        in which a PBCH or a primary or secondary synchronous signal is        transmitted within the same subframe, UE does not receive a        PDSCH RB transmitted in the antenna port 5, 7, 8, 9, 10, 11, 12,        13 or 14 in the corresponding 2 PRBs.    -   UE does not receive a PDSCH RB transmitted in the antenna port 7        to which distributed VRB resource allocation has been assigned.    -   UE may skip the decoding of a transport block if it does not        receive all of allocated PDSCH RBs. If the UE skips the        decoding, a physical layer indicates that the transport block        has not been successfully decoded for a higher layer.

In the case of the frame structure type 2,

-   -   UE does not receive a PDSCH RB transmitted in the antenna port 5        even in any subframe in which the number of OFDM symbols for a        PDCCH having a common CP is 4.    -   If any one of 2 PRBs to which a VRB pair is mapped overlaps a        frequency in which a PBCH is transmitted within the same        subframe, UE does not receive a PDSCH RB transmitted in the        antenna port 5 in the corresponding 2 PRBs.    -   If any one of 2 PRBs to which a VRB pair is mapped overlaps a        frequency in which a primary or secondary synchronous signal is        transmitted within the same subframe, UE does not receive a        PDSCH RB transmitted in the antenna port 7, 8, 9, 10, 11, 12, 13        or 14 in the corresponding 2 PRBs.    -   If a common CP is configured, UE does not receive a PDSCH in the        antenna port 5 in which distributed VRB resource allocation has        been assigned within a special subframe in an uplink-downlink        configuration #1 or #6.    -   UE does not receive a PDSCH transmitted in the antenna port 7 to        which distributed VRB resource allocation has been assigned.    -   UE may skip the decoding of a transport block if it does not        receive all of allocated PDSCH RBs. If the UE skips the        decoding, a physical layer indicates that the transport block        has not been successfully decoded for a higher layer.

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by a C-RNTI, the UE decodes the PDCCH and a correspondingPDSCH according to each combination defined in Table 6 below. The PDSCHcorresponding to the PDCCH(s) is scrambling-initialized by the C-RNTI.

If a CIF for a serving cell is configured in UE or UE is configured by ahigher layer so that it decodes a PDCCH with CRC scrambled by a C-RNTI,the UE decodes the PDSCH of a serving cell indicated by a CIF valuewithin the decoded PDCCH.

When UE of the transmission mode 3, 4, 8 or 9 receives DCI format 1Aassignment, the UE assumes that PDSCH transmission is related to atransport block 1 and a transport block 2 is disabled.

If UE is set as the transmission mode 7, a UE-specific reference signalcorresponding to a PDCCH(s) is scrambling-initialized by a C-RNTI.

If an extended CP is used in downlink, UE does not support thetransmission mode 8.

If UE is set as the transmission mode 9, when the UE detects a PDCCHwith CRC scrambled by a C-RNTI on which the DCI format 1A or 2C intendedfor the UE is carried, the UE decodes a corresponding PDSCH in asubframe indicated by a higher layer parameter“mbsfn-SubframeConfigList.” However, the subframe configured by a higherlayer to decode a PMCH or, the subframe configured by a higher layer tobe part of a PRS occasion and the PRS occasion is configured only withinan MBSFN subframe and the length of a CP used in a subframe #0 is acommon CP is excluded.

Table 10 illustrates a PDCCH and PDSCH configured by a C-RNTI.

TABLE 10 METHOD FOR SENDING PDSCH TRANSMISSION DCI CORRESPONDING TO MODEFORMAT SEARCH SPACE PDCCH Mode 1 DCI format common and a single antennaport, a port 0 1A UE-specific by a C-RNTI DCI format 1 UE-specific by aa single antenna port, a port 0 C-RNTI Mode 2 DCI format common andtransmit diversity 1A UE-specific by a C-RNTI DCI format 1 UE-specificby a transmit diversity C-RNTI Mode 3 DCI format common and transmitdiversity 1A UE-specific by a C-RNTI DCI format UE-specific by a largedelay CDD or transmit 2A C-RNTI diversity Mode 4 DCI format common andtransmit diversity 1A UE-specific by a C-RNTI DCI format 2 UE-specificby a closed-loop spatial C-RNTI multiplexing or transmit diversity Mode5 DCI format common and transmit diversity 1A UE-specific by a C-RNTIDCI format UE-specific by a multi-user MIMO 1D C-RNTI Mode 6 DCI formatcommon and transmit diversity 1A UE-specific by a C-RNTI DCI formatUE-specific by a closed-loop spatial 1B C-RNTI multiplexing using asingle transport layer Mode 7 DCI format common and If the number ofPBCH 1A UE-specific by a antenna ports is 1, a single C-RNTI antennaport, a port 0 is used, and if not, transmit diversity DCI format 1UE-specific by a Single antenna port, a port 5 C-RNTI Mode 8 DCI formatcommon and If the number of PBCH 1A UE-specific by a antenna ports is 1,a single C-RNTI antenna port, a port 0 is used, and if not, transmitdiversity DCI format UE-specific by a dual layer transmission, 2B C-RNTIports 7 and 8 or a single antenna port, a port 7 or 8 Mode 9 DCI formatcommon and Non-MBSFN subframe: if 1A UE-specific by a the number of PBCHC-RNTI antenna ports is 1, a single antenna port, a port 0 is used, andif not, transmit diversity MBSFN subframe: a single antenna port, a port7 DCI format UE-specific by a layer transmission up to a 2C C-RNTImaximum of 8, ports 7-14

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by an SPS C-RNTI, the UE decodes a PDCCH of a primary celland a corresponding PDSCH of the primary cell according to eachcombination defined in Table 7 below. If a PDSCH is transmitted withouta corresponding PDCCH, the same PDSCH-related configuration is applied.The PDSCH corresponding to the PDCCH and the PDSCH not having a PDCCH isscrambling-initialized by the SPS C-RNTI.

If UE is set as the transmission mode 7, a PDCCH(s) and a correspondingUE-specific reference signal is scrambling-initialized by an SPS C-RNTI.

If UE is set as the transmission mode 9, when the UE detects a PDCCHwith CRC scrambled by an SPS C-RNTI on which the DCI format 1A or 2Cintended for the UE is carried or a PDSCH configured without a PDCCHintended for the UE, the UE decodes a corresponding PDSCH in a subframeindicated by a higher layer parameter “mbsfn-SubframeConfigList.”However, the subframe configured a higher layer to decode a PMCH or, thesubframe configured by a higher layer to be part of a PRS occasion andthe PRS occasion is configured only within an MBSFN subframe and the CPlength used in a subframe #0 is a common CP is excluded.

Table 11 illustrates a PDCCH and PDSCH configured by an SPS C-RNTI.

TABLE 11 METHOD FOR TRANS- SENDING PDSCH MISSION DCI CORRESPONDING TOMODE FORMAT SEARCH SPACE PDCCH Mode 1 DCI format common and a singleantenna port, a 1A UE-specific by a port 0 C-RNTI DCI format 1UE-specific by a a single antenna port, a C-RNTI port 0 Mode 2 DCIformat common and transmit diversity 1A UE-specific by a C-RNTI DCIformat 1 UE-specific by a transmit diversity C-RNTI Mode 3 DCI formatcommon and transmit diversity 1A UE-specific by a C-RNTI DCI formatUE-specific by a transmit diversity 2A C-RNTI Mode 4 DCI format commonand transmit diversity 1A UE-specific by a C-RNTI DCI format 2UE-specific by a transmit diversity C-RNTI Mode 5 DCI format common andtransmit diversity 1A UE-specific by a C-RNTI Mode 6 DCI format commonand transmit diversity 1A UE-specific by a C-RNTI Mode 7 DCI formatcommon and a single antenna port, a 1A UE-specific by a port 5 C-RNTIDCI format 1 UE-specific by a a single antenna port, a C-RNTI port 5Mode 8 DCI format common and a single antenna port, a 1A UE-specific bya port 7 C-RNTI DCI format UE-specific by a a single antenna port, a 2BC-RNTI port 7 or 8 Mode 9 DCI format common and a single antenna port, a1A UE-specific by a port 7 C-RNTI DCI format UE-specific by a a singleantenna port, a 2C C-RNTI port 7 or 8

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by a temporary C-RNTI and is configured to not decode aPDCCH with CRC scrambled by a C-RNTI, the UE decodes a PDCCH and acorresponding PDSCH according to a combination defined in Table 8. ThePDSCH corresponding to the PDCCH(s) is scrambling-initialized by thetemporary C-RNTI.

Table 12 illustrates a PDCCH and a PDSCH configured by a temporaryC-RNTI.

TABLE 12 DCI METHOD FOR SENDING PDSCH FORMAT SEARCH SPACE CORRESPONDINGTO PDCCH DCI format common and If the number of PBCH antenna 1AUE-specific by a ports is 1, a single antenna temporary C-RNTI port, aport 0 is used, and if not, transmit diversity DCI UE-specific by a Ifthe number of PBCH antenna format 1 temporary C-RNTI ports is 1, asingle antenna port, a port 0 is used, and if not, transmit diversity

UE Procedure for PUSCH Transmission

UE is semi-statically configured through higher layer signaling so thatit performs PUSCH transmission signaled through a PDCCH according to anyone of two types of uplink transmission modes 1 and 2 defined in Table13 below. If the UE is configured by a higher layer so that it decodes aPDCCH with CRC scrambled by a C-RNTI, the UE decodes the PDCCH accordingto a combination defined in Table 9 and sends the corresponding PUSCH.The PUSCH transmission corresponding to the PDCCH(s) and the PUSCHretransmission for the same transport block is scrambling-initialized bythe C-RNTI. The transmission mode 1 is a default uplink transmissionmode until an uplink transmission mode is assigned in the UE by higherlayer signaling.

When UE is configured as the transmission mode 2 and receives a DCIformat 0 uplink scheduling grant, the UE assumes that PUSCH transmissionis related to a transport block 1 and a transport block 2 is disabled.

Table 13 illustrates a PDCCH and a PUSCH configured by a C-RNTI.

TABLE 13 METHOD FOR TRANS- SENDING PUSCH MISSION DCI CORRESPONDING TOMODE FORMAT SEARCH SPACE PDCCH mode 1 DCI format 0 common and a singleantenna port, a UE-specific by a port 10 C-RNTI mode 2 DCI format 0common and a single antenna port, a UE-specific by a port 10 C-RNTI DCIformat 4 UE-specific by a closed-loop spatial C-RNTI multiplexing

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by a C-RNTI and also configured to receive a random accessprocedure started by a PDCCH order, the UE decodes the PDCCH accordingto a combination defined in Table 10 below.

Table 14 illustrates a PDCCH set as a PDCCH order for starting a randomaccess procedure.

TABLE 14 DCI FORMAT SEARCH SPACE DCI format 1A common and UE-specific bya C-RNTI

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by an SPS C-RNTI, the UE decodes the PDCCH according to acombination defined in Table 11 below and sends a corresponding PUSCH.The PUSCH transmission corresponding to the PDCCH(s) and the PUSCHretransmission for the same transport block is scrambling-initialized bythe SPS C-RNTI. PUSCH retransmission for the same transport block as theminimum transmission of a PUSCH without a corresponding PDCCH isscrambling-initialized by an SPS C-RNTI.

Table 15 illustrates a PDCCH and a PUSCH configured by an SPS C-RNTI.

TABLE 15 METHOD FOR TRANS- SENDING PUSCH MISSION DCI CORRESPONDING MODEFORMAT SEARCH SPACE TO PDCCH mode 1 DCI format 0 common and a singleantenna port, a UE-specific by a port 10 C-RNTI mode 2 DCI format 0common and a single antenna port, a UE-specific by a port 10 C-RNTI

If UE is configured by a higher layer so that it decodes a PDCCHscrambled by a temporary C-RNTI regardless of whether the UE has beenconfigured to decode a PDCCH with CRC scrambled by a C-RNTI, the UEdecodes the PDCCH according to a combination defined in Table 12 andsends a corresponding PUSCH. The PUSCH corresponding to the PDCCH(s) isscrambling-initialized by the temporary C-RNTI.

If a temporary C-RNTI is set by a higher layer, PUSCH transmissioncorresponding to a random access response grant and PUSCH retransmissionfor the same transport block are scrambled by the temporary C-RNTI. Ifnot, the PUSCH transmission corresponding to the random access responsegrant and the PUSCH retransmission for the same transport block arescrambled by a C-RNTI.

Table 16 illustrates a PDCCH configured by a temporary C-RNTI.

TABLE 16 DCI FORMAT SEARCH SPACE DCI format 0 common

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by a TPC-PUCCH-RNTI, the UE decodes the PDCCH according toa combination defined in Table 13 below. In Table 13, indication “3/3A”means that UE receives the DCI format 3 or a DCI format depending on aconfiguration.

Table 17 illustrates a PDCCH configured by a TPC-PUCCH-RNTI.

TABLE 17 DCI FORMAT SEARCH SPACE DCI formats 3/3A common

If UE is configured by a higher layer so that it decodes a PDCCH withCRC scrambled by a TPC-PUSCH-RNTI, the UE decodes the PDCCH according toa combination defined in Table 14 below. In Table 14, indication “3/3A”includes that UE receives the DCI format 3 or a DCI format depending ona configuration.

Table 18 illustrates a PDCCH configured by a TPC-PUSCH-RNTI.

TABLE 18 DCI FORMAT SEARCH SPACE DCI formats 3/3A common

Relay Node (RN)

In a relay node, data transmitted/received between an eNB and UE istransferred through two different links (i.e., a backhaul link and anaccess link). An eNB may include a donor cell. A relay node iswirelessly connected to a radio access network through a donor cell.

In relation to the use of the bandwidth (or spectrum) of a relay node, acase where a backhaul link operates in the same frequency bandwidth asthat of an access link is called an “in-band”, and a case where abackhaul link and an access link operate in different frequencybandwidths is called an “out-band.” In both the in-band and theout-band, UE (hereinafter called “legacy UE”) operating in accordancewith an existing LTE system (e.g., release-8) needs to be able to accessa donor cell.

A relay node may be divided into a transparent relay node and anon-transparent relay node depending on whether UE recognizes a relaynode. The term “transparent” means whether UE communicates with anetwork through a relay node is not recognized. The term“non-transparent” means whether UE communicates with a network through arelay node is recognized.

In relation to control of a relay node, a relay node may be divided intoa relay node formed as part of a donor cell and a relay nodeautonomously controlling a cell.

A relay node formed as part of a donor cell may have a relay nodeidentity (relay ID), but does not have its own cell identity.

If at least part of Radio Resource Management (RRM) is controlled by aneNB belonging to a donor cell, it is called a relay node formed as partof a donor cell although the remaining parts of the RRM are placed inthe relay node. Such a relay node may support legacy UE. For example,various types of smart repeaters, decode-and-forward relays, and secondlayer (L2) relay nodes and a Type-2 relay node correspond to such arelay node.

In the case of a relay node autonomously controlling a cell, the relaynode controls one or a plurality of cells, and a unique physical layercell identity is provided to each of the cells controlled by the relaynode. Furthermore, the cells controlled by the relay node may use thesame RRM mechanism. From a viewpoint of UE, there is no differencebetween access to a cell controlled by a relay node and access to a cellcontrolled by a common eNB. A cell controlled by such a relay node maysupport legacy UE. For example, a self-backhauling relay node, a thirdlayer (L3) relay node, a Type-1 relay node, and a Type-1a relay nodecorrespond to such a relay node.

The Type-1 relay node is an in-band relay node and controls a pluralityof cells, and each of the plurality of cells is seen by UE as a separatecell different from a donor cell. Furthermore, the plurality of cellshas different physical cell IDs (this is defined in LTE release-8), andthe relay node may send its own synchronization channel and referencesignal. In the case of one cell operation, UE directly may receivescheduling information and HARQ feedback from a relay node and send itsown control channels (e.g., a Scheduling Request (SR), a CQI, andACK/NACK) to the relay node. Furthermore, the Type-1 relay node is seenby legacy UE (i.e., UE operating in accordance with an LTE release-8system) as a legacy eNB (i.e., an eNB operating in accordance with anLTE release-8 system). That is, the Type-1 relay node has backwardcompatibility. Meanwhile, the Type-1 relay node is seen by UEs operatingin accordance with an LTE-A system as an eNB different from a legacyeNB, thereby being capable of providing improved performance.

The Type-1a relay node has the same characteristics as the Type-1 relaynode except that it operates in an out-band. The operation of theType-1a relay node may be configured so that an influence on a firstlayer (L) operation is minimized.

The Type-2 relay node is an in-band relay node, and it does not have aseparate physical cell ID and thus does not form a new cell. The Type-2relay node is transparent to legacy UE, and the legacy UE does notrecognize the presence of the Type-2 relay node. The Type-2 relay nodemay send a PDSCH, but does not send at least CRS and PDCCH.

In order to operate a relay node in in-band, some resources in atime-frequency domain may need to be reserved for a backhaul link andmay be configured so that they are not used for an access link. This iscalled resource partitioning.

A known principle in resource partitioning in a relay node may bedescribed as follows. Backhaul downlink and access downlink may bemultiplexed according to a Time Division Multiplexing (TDM) method onone carrier frequency (i.e., only one of a backhaul downlink and anaccess downlink in a specific time is activated). Likewise, backhauluplink and access uplink may be multiplexed according to a TDM method onone carrier frequency (i.e., only one of a backhaul uplink and an accessuplink in a specific time is activated).

In backhaul link multiplexing in FDD, backhaul downlink transmission maybe performed in a downlink frequency bandwidth, and the transmission ofa backhaul uplink may be performed in an uplink frequency bandwidth. Inbackhaul link multiplexing in TDD, backhaul downlink transmission may beperformed in a downlink subframe of an eNB and a relay node, and thetransmission of a backhaul uplink may be performed in an uplink subframeof an eNB and a relay node.

In the case of an in-band relay node, for example, when the reception ofa backhaul downlink from an eNB and the transmission of an accessdownlink to UE are performed in the same frequency bandwidth at the sametime, signal interference may be generated in the reception end of arelay node due to a signal transmitted by the transmission end of therelay node. That is, signal interference or RF jamming may be generatedin the RF front end of the relay node. Likewise, when the transmissionof a backhaul uplink to an eNB and the reception of an access uplinkfrom UE are performed in the same frequency bandwidth at the same time,signal interference may be generated.

Accordingly, in order for a relay node to send/receive signals in thesame frequency bandwidth at the same time, a sufficient separation needsto be provided between a reception signal and a transmission signal(e.g., that the reception signal and the transmission signal need to besufficiently separated geographically, such as that a transmissionantenna and a reception antenna are installed on the ground and in thegrave, respectively).

One method for solving such signal interference is to allow a relay nodeto operate in such a way as not to send a signal to UE while receiving asignal from a donor cell. That is, a gap is generated in transmissionfrom the relay node to the UE, and the UE (including legacy UE) isconfigured to not expect any transmission from the relay node during thegap. Such a gap may be configured by configuring a Multicast BroadcastSingle Frequency Network (MBSFN) subframe.

FIG. 18 illustrates the segmentation of a relay node resource in awireless communication system to which an embodiment of the presentinvention may be applied.

In FIG. 18, a first subframe is a common subframe, and a downlink (i.e.,access downlink) control signal and data are transmitted from a relaynode to UE in the first subframe. In contrast, a second subframe is anMBSFN subframe, and a control signal is transmitted from the relay nodeto the UE in the control region of the downlink subframe, but notransmission is performed from the relay node to the UE in the remainingregion of the downlink subframe. In this case, since legacy UE expectsthe transmission of a PDCCH in all downlink subframes (i.e., a relaynode needs to provide support so that legacy UEs within the region ofthe relay node perform measurement functions by receiving a PDCCH everysubframe), the PDCCH needs to be transmitted in all downlink subframesfor the correct operation of the legacy UE. Accordingly, the relay nodedoes not perform backhaul downlink reception, but needs to performaccess downlink transmission in the first N (N=1, 2 or 3) OFDM symbolperiod of a subframe (i.e., the second subframe) on the subframeconfigured for downlink (i.e., backhaul downlink) transmission from aneNB to the relay node. For this, the relay node may provide backwardcompatibility to serving legacy UE because a PDCCH is transmitted fromthe relay node to the UE in the control region of the second subframe.The relay node may receive transmission from the eNB while notransmission is performed from the relay node to the UE in the remainingregion of the second subframe. Accordingly, access downlink transmissionand backhaul downlink reception may not be performed at the same time inan in-band relay node through such a resource partitioning method.

The second subframe using an MBSFN subframe is described in detail. Thecontrol region of the second subframe may be said to be a relay nodenon-hearing period. The relay node non-hearing interval means aninterval in which a relay node does not receive a backhaul downlinksignal, but sends an access downlink signal. The interval may beconfigured to have a 1, 2 or 3 OFDM length, such as that describedabove. A relay node performs access downlink transmission to UE in arelay node non-hearing interval, but may perform backhaul downlinkreception from an eNB in the remaining region. In this case, time istaken for the relay node to switch from transmission mode to receptionmode because the relay node is unable to perform transmission/receptionin the same frequency bandwidth at the same time. Accordingly, a GuardTime (GT) needs to be configured so that the relay node switches totransmission/reception mode in the first some interval of a backhauldownlink reception region. Likewise, a guard time for enabling the relaynode to switch to reception/transmission mode may be configured althoughthe relay node operates in such a way as to receive a backhaul downlinkfrom the eNB and to send an access downlink to the UE. The length ofsuch a guard time may be set as a value in a time domain. For example,the length of the guard time may be set as a k (k≥1) time sample (Ts)value or may be set as one or more OFDM symbol length. Alternatively,relay node backhaul downlink subframes may be contiguously configured,or the guard time of the last part of a subframe may not be defined orconfigured according to a specific subframe timing alignmentrelationship. Such a guard time may be defined only in a frequencydomain configured for backhaul downlink subframe transmission in orderto maintain backward compatibility (if a guard time is configured in anaccess downlink interval, legacy UE cannot be supported). In a backhauldownlink reception interval other than the guard time, the relay nodemay receive a PDCCH and a PDSCH from the eNB. This may be represented bya relay-PDCCH (R-PDCCH) and a relay-PDSCH (R-PDSCH) in the meaning of arelay node-dedicated physical channel.

Quasi Co-Located (QCL) Between Antenna Ports

Quasi co-located and quasi co-location (QC/QCL) may be defined asfollows.

If two antenna ports have a QC/QCL relation (or subjected to QC/QCL), UEmay assume that the large-scale property of a signal transferred throughone antenna port may be inferred from a signal transferred through theother antenna port. In this case, the large-scale property includes oneor more of Delay spread, Doppler spread, Frequency shift, Averagereceived power, and Received timing.

Furthermore, the following may be defined. Assuming that two antennaports have a QC/QCL relation (or subjected to QC/QCL), UE may assumethat the large-scale property of a channel of which one symbol istransferred through one antenna port may be inferred from a wirelesschannel of which one symbol is transferred through the other antennaport. In this case, the large-scale property includes one or more ofDelay spread, Doppler spread, Doppler shift, Average gain, and Averagedelay.

That is, if two antenna ports have a QC/QCL relation (or subjected toQC/QCL), it means that the large-scale property of a wireless channelfrom one antenna port is the same as the large-scale property of awireless channel from the other antenna port. Assuming that a pluralityof antenna ports in which an RS is transmitted is taken intoconsideration, if antenna ports on which two types of different RSs aretransmitted have a QCL relation, the large-scale property of a wirelesschannel from one antenna port may be replaced with the large-scaleproperty of a wireless channel from the other antenna port.

In this specification, the QC/QCL-related definitions are notdistinguished. That is, the QC/QCL concept may comply with one of thedefinitions. In a similar other form, the QC/QCL concept definition maybe changed in a form in which antenna ports having an established QC/QCLassumption may be assumed to be transmitted at the same location (i.e.,co-location) (e.g., UE may assume antenna ports to be antenna portstransmitted at the same transmission point). The spirit of the presentinvention includes such similar modifications. In an embodiment of thepresent invention, the QC/QCL-related definitions are interchangeablyused, for convenience of description.

In accordance with the concept of the QC/QCL, UE may not assume the samelarge-scale property between wireless channels from correspondingantenna ports with respect to non-QC/QCL antenna ports. That is, in thiscase, UE may perform independent processing on timing acquisition andtracking, frequency offset estimation and compensation, delayestimation, and Doppler estimation for each configured non-QC/QCLantenna port.

There are advantages in that UE may perform the following operationsbetween antenna ports capable of an assuming QC/QCL:

-   -   With respect to the Delay spread and Doppler spread, UE may        identically apply the results of a power-delay profile, Delay        spread and Doppler spectrum, and Doppler spread estimation for a        wireless channel from any one antenna port to a Wiener filter        which is used upon channel estimation for a wireless channel        from other antenna ports.    -   With respect to the Frequency shift and received timing, UE may        perform time and frequency synchronization on any one antenna        port and then apply the same synchronization to the demodulation        of other antenna ports.    -   With respect to the Average received power, UE may average        reference signal received power (RSRP) measurement for two or        more antenna ports.

For example, if a DMRS antenna port for downlink data channeldemodulation has been subjected to QC/QCL with the CRS antenna port of aserving cell, UE may apply the large-scale property of a wirelesschannel estimated from its own CRS antenna port upon channel estimationthrough the corresponding DMRS antenna port, in the same manner, therebyimproving reception performance of a DMRS-based downlink data channel.

The reason for this is that an estimation value regarding a large-scaleproperty may be more stably obtained from a CRS because the CRS is areference signal that is broadcasted with relatively high density everysubframe and in a full bandwidth. In contrast, a DMRS is transmitted ina UE-specific manner with respect to a specific scheduled RB, and theprecoding matrix of a precoding resource block group (PRG) unit that isused by an eNB for transmission may be changed. Thus, a valid channelreceived by UE may be changed in a PRG unit. Accordingly, although aplurality of PRGs has been scheduled in the UE, performancedeterioration may occur when the DMRS is used to estimate thelarge-scale property of a wireless channel over a wide band.Furthermore, a CSI-RS may also have a transmission cycle ofseveral˜several tens of ms, and each resource block has also low densityof 1 resource element for each antenna port in average. Accordingly, theCSI-RS may experience performance deterioration if it is used toestimate the large-scale property of a wireless channel.

That is, UE may perform the detection/reception, channel estimation, andchannel state report of a downlink reference signal through a QC/QCLassumption between antenna ports.

Buffer Status Reporting (BSR)

A buffer status reporting procedure may be used to provide informationregarding an amount of data available (or valid) for transmission fromUL buffers of a UE to a serving eNB. An RRC may control BSR reporting byconfiguring two timers, and here, the two timers may beperiodicBSR-Timer and retxBSR-Timer. Also, the RRC may control BSRreporting by signaling a logical channel group (logicalChannelGroup,LCG) for selectively allocating a logical channel for the LGC.

For the BSR procedure, the UE should consider all the radio bearerswhich are not suspended. Also, here, the UE may consider suspended radiobearers.

The BSR may be triggered when any one of the following events occurs.

-   -   In case where UL data (regarding a logical channel which belongs        to the LCG) is transmittable from an RLC entity or a PDCP        entity, in case where data belonging to a logical channel having        priority higher than priority of a logical channel that belongs        to a specific LCG is already transmittable or in case where        there is no transmittable data for (or through) any one of        logical channels belonging to the LCG (that is, in case where        BSR corresponds to/or is designated as “regular BSR” described        hereinafter).    -   In case where UL resources are allocated and the number of        padding bits is equal to or greater than a size obtained by        adding a BSR MAC control element and a subheader thereof (that        is, in case where the BSR corresponds to/or is designated as        “Padding BSR” described hereinafter)    -   In case where retxBSR-Timer expires and the UE has transmittable        data regarding a logical channel that belongs to the LCG (that        is, in case where BSR corresponds to/designated as “Regular        BSR”)    -   In case where periodic BSR-Timer expires (That is, in case where        BSR corresponds to/is designated as “Periodic BSR” described        hereinafter)

In the case of Regular and Periodic BSR:

-   -   If one or more LCGs have transmittable data within a TITI in        which the BSR is transmitted: Long BSR is reported.    -   In other cases, short BSR is reported.

In the case of Padding BSR:

1) If the number of padding bits is equal to or greater than a sizeobtained by adding the short BSR and a subheader thereof and smallerthan a size obtained by adding a long BSR and a subheader thereof

-   -   In case where one or more LCGs have data transmittable within a        TTI in which the BSR is transmitted: a truncated BSR of the LCG        having a logical channel with highest priority in which        transmittable data is transmitted is reported.    -   In other cases: short BSR is reported.

2) Besides, in case where the number of padding bits is equal to orgreater than a size obtained by adding a long BSR and a subheaderthereof: the long BSR is reported.

In case where at least one BSR is triggered and determined that it isnot canceled in a BSR procedure:

1) In case where the UE has UL resource allocated for new transmissionin a corresponding TH:

-   -   It instructs multiplexing and assembly procedure to generate a        BSR MAC control element.    -   periodicBSR-Timer is started or re-started, except for a case        where every generated BSR is a truncated BSR.    -   retxBSR-Timer is started or re-started.

2) Besides, in case where a Regular BSR is triggered:

-   -   In case where a UL grant is not configured or a regular BSR is        not triggered due to data transmittable through a logical        channel (here, the logical channel is a channel set in SR        masking (logicalChannelSR-Mask) by an upper layer): Scheduling        request is triggered.

When the regular BSR and the periodic BSR has priority over a paddingBSR, even when a plurality of events triggering BSR until the BSR istransmittable occur, a MAC PDU includes a maximum of one MAC BSR controlelement. When the UE is instructed to approve regarding transmission ofnew data of any UL-SCH, the UE may start or re-start retxBSR-Timer.

All the triggered BSRs may accommodate every pending transmission dataof UL grant of a subframe but may be canceled when it is not sufficientfor additionally accommodating the sum of a BSR MAC control element anda subheader thereof. All triggered BSRs may be canceled when a BSR isincluded in the MAC PDU for transmission.

The UE may transmit a maximum of one regular/periodic BSR within oneTTI. If the UE is requested to transmit a plurality of MAC PDUs withinone TII, the UE may include a padding BAR in any one of MAC PDUs notincluding the regular/periodic BSR.

All BSRs transmitted within one TI may always reflect a buffer stateafter all MAC PDUs configured for the TI are transmitted. Each LCG mayreport a maximum of one buffer state value, and the value may bereported in every BSR report buffer state for the LCGs. The padding BSRis not permitted to cancel a triggered regular/periodic BSR. The paddingBSR is triggered only for a specific MAC PDU, and the trigger iscanceled when the MAC PDU is configured.

D2D (Device-to-Device) Communication

FIG. 19 shows elements regarding a scheme of direct communicationbetween terminals (D2D).

In FIG. 19, the UE refers to a terminal of a user, and in case wherenetwork equipment such as an eNB transmits and receives a signalaccording to a communication scheme with a UE, the corresponding networkequipment may also be regarded as a UE. Hereinafter, UE1 may select aresource unit corresponding to a specific resource within a resourcepool indicating a set of resources and operates to transmit a D2D signalusing the corresponding resource unit. A UE2, which is a receiving UEthereof, configures a resource pool in which a UE1 may transmit a signaland detects a signal of the UE1 in the corresponding pool. Here, theresource pool may be notified by a BS when the UE1 is within aconnection range of the BS, and may be informed by another UE ordetermined as a predetermined resource when it is outside the connectionrange of the BS. In general, a resource pool may include a plurality ofresource units, and each UE may select one or a plurality of resourceunits to use the same to transmit a D2D signal thereof.

FIG. 20 shows an embodiment of configuration of resource units.

Referring to FIG. 20, a total of N_F*N_T resource units may be definedby dividing the entire frequency resources into N_F and the entire timeresources into N_T. Here, it may be expressed that the correspondingresource pool is repeated at intervals of N_T subframes.Characteristically, one resource unit may appear repeatedly periodicallyas shown in the drawing. Or, an index of a physical resource unit towhich one logical resource unit is mapped may change in a predeterminedpattern over time in order to obtain a diversity effect in the time orfrequency domain. In this resource unit structure, the resource pool mayrefer to a set of resource units which may be used by the UE to transmitthe D2D signal.

The resource pools described above may be subdivided into various kinds.First, the resource pools may be divided according to the content of aD2D signal transmitted in each resource pool. For example, the contentof the D2D signal may be divided as follows, and a separate resourcepool may be configured for each signal.

Scheduling assignment (SA): A signal including a position of a resourceused for transmission of a D2D data channel performed by eachtransmitting UE, and information such as a modulation and coding scheme(MCS) required for demodulating other data channels, a MIMO transmissionscheme and/or timing advance, and the like. This signal may also bemultiplexed and transmitted along with the D2D data on the same resourceunit. In this disclosure, the SA resource pool may refer to a pool ofresources in which the SA is multiplexed and transmitted with the D2Ddata, and may also be referred to as a D2D control channel.

D2D data channel: A resource pool used by a transmitting UE to transmituser data using a resource designated through an SA. When it is possibleto be multiplexed and transmitted together with the D2D data on the sameresource unit, only a D2D data channel without the SA information may betransmitted in the resource pool for the D2D data channel. In otherwords, the resource element, which was used to transmit the SAinformation on the individual resource unit in the SA resource pool, maybe used to transmit D2D data in the D2D data channel resource pool.

Discovery channel: A resource pool for a message to which a transmittingUE transmits information such as its own ID, or the like, so that aneighboring UE may discover the transmitting UE.

Contrary to the above case, even when the content of the D2D signal isthe same, different resource pools may be used depending on thetransmission/reception properties of the D2D signal. For example, eventhe same D2D data channel or a discovery message may be classified intodifferent resource pools depending on a transmission timingdetermination scheme of the D2D signal (for example, whether it istransmitted at a time point when a synchronization reference signal isreceived or whether it is transmitted by applying a certain timingadvance at the corresponding time point), a resource allocation scheme(e.g., whether the eNB designates transmission resource of an individualsignal to an individual transmitting UE or whether an individualtransmitting UE selects an individual signaling transmission resource byitself from the pool), a signal format (e.g., the number of symbols ofeach D2D signal which occupy one subframe, or the number of subframesused for transmission of one D2D signal), signal strength from the eNB,strength of transmission power of the D2D UE, and the like.

In this disclosure, for the purposes of description, a method in whichthe eNB directly indicates a transmission resource of a D2D transmittingUE in D2D communication will be called/defined as Mode 1 and a method inwhich a transmission resource region is set in advance, the eNBdesignates a transmission resource region, and a UE directly selects atransmission resource will be called/defined as Mode 2. In the case ofD2D discovery, a case in which the eNB directly indicates resource willbe called/defined as Type 2 and a case in which the UE directly selectstransmission resource in a preset resource region or a resource regionindicated by the eNB will be called/defined as Type 1.

The afore-mentioned D2D may also be called a sidelink, the SA may becalled a physical sidelink control channel (PSCCH), a D2Dsynchronization signal may be called a sidelink synchronization signal(SSS), a control channel for transmitting most basic information priorto D2D communication transmitted together with the SSS may be called aphysical sidelink broadcast channel (PSBCH), or a PD2DSCH (Physical D2Dsynchronization channel) by a different name. A signal indicating that aspecific terminal is in its vicinity, which may include an ID of aspecific terminal, may be called a physical sidelink discovery channel(PSDCH).

In D2D of Rel. 12, only a D2D communication UE transmits the PSBCHtogether with the SSS, and therefore, measurement of the SSS isperformed using a DMRS of the PSBCH. An out-coverage UE measures theDMRS of the PSBCH and measures a reference signal received power (RSRP)of the signal to determine whether the UE will become a synchronizationsource.

V2X (Vehicle-to-Vehicle/Infrastructure/Pedestrian) Communication

In the present invention, V2X communication-related technologiesproviding the following service types will be described. Three typicalservice types of V2X communication are as follows.

-   -   V2V (vehicle-to-vehicle): Communication between vehicles    -   V2I (vehicle-to-infrastructure): Communication between a vehicle        and a roadside unit (RSU) which is implemented in an eNB or a        stationary UE    -   V2P (vehicle-to-pedestrian): Communication between a vehicle and        a device carried by an individual (pedestrian, cyclist, driver        or passenger)

FIGS. 21 and 22 show V2X communication according to an embodiment of thepresent invention. More specifically, FIG. 21 shows V2V and V2Icommunication according to an embodiment of the present invention, andFIG. 22 shows V2P communication according to an embodiment of thepresent invention.

A vehicle may perform V2X communication to transmit variousinformation/messages. In particular, V2X communication may be performedfor the purpose of informing about a specific situation such as anaccident.

For example, referring to FIG. 21, when a vehicle accident occurs at aspecific point, the accident vehicle may transmit a warning message to aneighboring vehicle to inform the occurrence of the accident. In thiscase, the accident vehicle may directly transmit a warning message(e.g., V2X message, cooperative awareness message (CAM)/decentralizedenvironmental notification message (DENM)) to a nearby vehicle, whichmay correspond to V2V communication. Alternatively, the accident vehiclemay transmit a warning message to a nearby vehicle through aninfrastructure network such as an LTE RSU, or the like, locatedtherearound, which may correspond to V2I communication.

Or, referring to FIG. 22, if it is predicted that a pedestrian and avehicle will approach each other at a rapid pace and collide with eachother, the corresponding vehicle may directly transmit a collisionwarning message to a terminal of the pedestrian, which may correspond toV2P communication. At this time, a receiver for receiving the message inthe V2P communication is not limited to the terminal of the pedestrianand may correspond to all terminals available for V2P communication suchas a terminal of a bicycle/vehicle driver or an occupant of abicycle/vehicle.

In this manner, the V2X communication may be performed for a specificpurpose such as to inform an emergency situation more rapidly, and amethod for operating V2X communication more effectively has beenactively discussed.

In this disclosure, various technologies for supporting V2Icommunication, which is more focused on V2I environment, are proposed.However, the corresponding technologies are not limited to the V2Ienvironment, and may be applied in the V2X communication environment inthe same/similar manner.

Hereinafter, for the purposes of description, it is assumed that anaccident occurs in a vehicle during driving as shown in FIG. 21 and anaccident vehicle (or a vehicle related to the accident) at an accidentoccurrence point informs surrounding cells about the accident situation.

Here, a specific cell (for example, an infrastructure network such as anRSU, etc.) which has received the accident situation may broadcast theaccident situation such that a terminal (for example, another vehicle ora pedestrian's terminal) may recognize the accident situation. Here, iftwo or more cells (e.g., three neighbor cells) are to receive theaccident situation, it is preferred that these cells broadcast theaccident situation according to a specific order and method, and in thiscase, coverage to which the accident situation is transmitted isextended.

However, in general, most neighbor cells are not synchronized (forexample, an asynchronous situation in which a timing difference is about±5 ms between cells), which may be referred to as an asynchronousnetwork environment. In such an asynchronous network environment, the UEmay be difficult to receive a signal transmitted from a neighbor cellother than its serving cell, or considerable latency is required foraccessing the corresponding neighbor cell from a cell search process toreceive a signal. Such delay may cause a serious problem if a warningmessage/information indicating the accident situation is to be promptlytransmitted to each terminal.

Thus, hereinafter, embodiments of a method in which a serving cell of aUE and an asynchronous neighbor cell effectively performbroadcast/multicast transmission to the corresponding UE in theasynchronous network environment and a specific operation of the UErelated thereto is proposed.

The following four embodiments may be derived depending on the extent towhich the network (NW) supports assistance signaling in order to assisttransmission of an I2V signal from a neighbor cell to the UE in theasynchronous network environment.

1. No NW-assistance

2. Partial NW-assistance with timing information

3. Partial NW-assistance with SIB relaying

4. Full NW-assistance

One or a plurality of the four embodiments described above may beapplied to V2X communication. When a plurality of embodiments amapplied, each embodiment may be defined as a specific mode, and V2X mayoperate in a specific mode defined for each situation. For example,the 1. NW-assistance embodiment may be defined as a mode 1, the 4. FullNW-assistance embodiment may be defined as a mode 4, and the V2Xcommunication may operate as the mode 4 in the case of transmitting ahigh priority warning message, and may operate in the mode 1 in the caseof transmitting a low priority warning message.

Hereinafter, the four embodiments will be sequentially described indetail. Also, hereinafter, for the purposes of description, both avehicle and a personally carried terminal that perform V2X communicationmay be referred to as a ‘UE’, and a serving cell of the corresponding UEmay be referred to as Cell A, a neighbor cell which is not synchronizedwith the serving cell (or an asynchronous neighbor cell) will bereferred to as Cell B. In addition, information, data, signals and/ormessages broadcast/multicast transmitted from the Cell B will bereferred to as ‘broadcast/multicast data’.

1. No NW-Assistance

The present embodiment proposes a method in which a UE performs most ofpreceding procedures for receiving broadcast/multicast data from Cell B,an asynchronous neighbor cell, by itself. In this embodiment, the UE mayreceive system information (e.g., SIB) transmitted from the Cell B toreceive broadcast/multicast data of the Cell B on a subjective basis.

For example, in order to receive broadcast/multicast data from the CellB, the UE, whose serving cell is the Cell A, may recognize by itselfwhether the broadcast/multicast data of Cell B (or potentialbroadcast/multicast) is transmitted. To this end, the cell B maytransmit specific system information (i.e., SIB) including itsbroadcast/multicast transmission schedule information to the UE, therebyinforming the UE about whether the broadcast/multicast data of the cellB is transmitted or not in advance.

The specific system information includes, as the broadcast/multicasttransmission schedule information of the cell B, whether to transmitbroadcast/multicast data, broadcast/multicast transmission timinginformation (for example, information regarding at which pointbroadcast/multicast transmission is to be performed, etc.), positioninformation of transmission resource (time/frequency resource) of thebroadcast/multicast data, RS configuration information for demodulatingthe broadcast/multicast data, information regarding whether MIMO isapplied, layer related information, link adaptation related informationsuch as MCS, or the like, QCL information and/or index information of asubframe including broadcast/multicast data, and the like.

The reason why the Cell B transmits broadcast/multicast transmissionschedule information through the system information such as SIB is toallow the UE to receive broadcast/multicast data with low latency fromthe Cell B even in an idle state (or state which is not RRC_CONNECTED).That is, as described above, in the V2X communication environment, it isvery important to transmit urgent information such as occurrence of anaccident to each UE as soon as possible, and in particular, in order forthe UE to rapidly receive broadcast/multicast data from a neighbor celleven in an idle state, the UE preferably receives schedule informationrelated to broadcast/multicast transmission of the neighbor cell throughsystem information such as SIB in advance.

In this case, the UE may receive the system information (for example,SIB) transmitted from the cell B by acquiring sync of the cell B even inthe idle state, and recognize whether broadcast/multicast data to bereceived is present on the basis of the received system information. Ifthe UE recognizes that broadcast/multicast data to be received from thecell B is present, the UE may receive the correspondingbroadcast/multicast data transmitted through (or using) resourceindicated by the broadcast/multicast transmission related informationincluded in the received system information.

In order for the UE to continuously receive the system information fromthe cell B (that is, in order to continuously monitor the cell B), it isnecessary to set a condition for determining which cell is to be thecell B in advance. Here, the Cell B is a cell for transmittingbroadcast/multicast data, and refers to a neighbor cell for transmittingsystem information including broadcast/multicast transmission scheduleinformation so that the UE may receive the corresponding signal.

In an embodiment, the UE may determine the Cell B on the basis of an RRMmeasurement result. In detail, the UE may perform RRM measurement suchas measurement of reference signal received power (RSRP) and measurementof reference signal received quality (RSRQ) for each cell and set a cellhaving the best RRM measurement value to the Cell B.

For example, the UE may perform RRM measurement for each cell and mayset a cell (first best cell) having the best RRM measurement to the CellB to receive the system information from the corresponding cell.Further, the UE may set a cell having a second best RRM measurementvalue (second best cell) and a cell having a third best RRM measurementvalue (third best cell) (in this case, a plurality of cells are set tothe Cell B) to receive the system information from the correspondingcells.

Here, the cell having the best RRM measurement value may be determinedas a cell having the best RRM measurement value (first best cell), acell having the second best RRM measurement value (second best cell),and a cell having the third best RRM measurement value (third bestcell), sequentially from among cells having the highest absolute valuewhen the UE aligns absolute values of the RRM measurement values (forexample, the RSRP measurement value and the RSRQ measurement value)measured by cells in descending order.

Alternatively, as in the afore-mentioned embodiment, a cell having thebest RRM measurement value may be determined on the basis of theabsolute value of the RRM measurement value, or a scheme of determininga cell having the best RRM measurement value on the basis of adifference value in the RRM measurement value with the Cell A as theserving cell of the UE. The reason is because, if the RRM measurement ofthe Cell A is large but the RRM measurement of the neighbor cell issmall, the UE may not be able to receive a broadcast signal from thecorresponding neighbor cell. Therefore, for example, the UE maydetermine a cell having the best RRM measurement value in the ascendingorder of the difference value from the RRM measurement value of the CellA.

Alternatively, the UE may determine a cell having the best RRMmeasurement value in consideration of both the absolute value of the RRMmeasurement value and the difference value of the RRM measurement value.In this case, the UE may set a cell having the best RRM measurementvalue on the basis of a result of substituting the absolute value of theRRM measurement value and the difference value of the RRM measurementvalue to a predefined specific function.

As described above, the operating conditions of the UE for setting theCell B are defined and the operation scenario, or the like, is includedin a test case of the UE, whereby whether or not the UE supports such anoperation may be verified through testing.

The UE having determined the Cell B according to the above-describedembodiment may acquire system information from the cell determined asthe Cell B and determine whether the Cell B performs broadcast/multicasttransmission. Accordingly, when the UE determines that thebroadcast/multicast transmission of the cell B is scheduled, the UE mayreceive and decode broadcast/multicast data transmitted from the Cell Bon the basis of the broadcast/multicast transmission scheduleinformation included in the system information.

At this time, the broadcast/multicast transmission of the Cell B may betransmitted in a DMRS-based PDSCH (DMRS-based PDSCH). Therefore, aspecific QCL (Quasi-Co-Locate) assumption may be required for the UE toreceive it.

In an embodiment, a direct QCL between the DMRS port and the CRStransmitted by the Cell B may be assumed. In another embodiment, a QCLbetween a specific CSI-RS B transmitted by the Cell B and the DMRS isassumed, and here, CSI-RS B configuration related information may beincluded in system information (for example, SIB) or may be provided tothe corresponding UE by the serving Cell A in advance through RRCsetting, or the like. To this end, the Cell B may transmit the CSI-RS Bconfiguration related information allowing assumption of the QCL in thebroadcast/multicast transmission to the Cell A through backhaulsignaling such as X2 signaling in advance. Alternatively, the Cell A maypreviously request the CSI-RS B configuration related information fromthe Cell B and the Cell B may transmit the corresponding information asa response to the request.

Alternatively, the broadcast/multicast transmission of the Cell B may beperformed according to a multimedia broadcast multicast services (MBMS)transmission scheme.

2. Partial NW-Assistance with Timing Information

The present embodiment proposes a method of performing a precedingprocedure for receiving broadcast/multicast data from the cell B, anasynchronous neighbor cell, and here, the preceding procedure isperformed by obtaining assistance from the Cell A as a serving cell.Particularly, in the present embodiment, the Cell A provides, to the UE,information regarding a timing at which the UE may receive systeminformation, as partial NW-assistance information to the UE about thetiming with which the UE may receive the system information from theCell B, thus assisting the UE receiving the broadcast/multicast data.

For example, the Cell A may provide indication information that the UEshould receive/decode system information (for example, SIB) transmittedfrom the Cell B at a specific time point to the UE through signalingsuch as DCI. Here, the corresponding indication information may includeasynchronous related auxiliary information such as reading as anasynchronous SF (subframe) boundary delayed by about 4 ms.

To this end, the Cell B may share broadcast/multicast transmissionschedule information with the Cell A through X2 signaling. Thebroadcast/multicast transmission schedule information transmittedthrough X2 signaling may indicate when/by which resource (i.e.,time/space/frequency resource) the cell B will transmitbroadcast/multicast data.

The broadcast/multicast transmission schedule information may mean thatthe eNB and/or the cell which receive the broadcast/multicasttransmission schedule information mute at the time and/or resource inwhich the Cell B transmits system information (that is, the eNB and/orthe cell should not transmit a signal using the same resource at thesame time as those of the Cell B), and thus, the broadcast/multicasttransmission schedule information may be transmitted in conjunction withCoMP-related signaling. For example, the broadcast/multicasttransmission schedule information may be transmitted in conjunction withsignaling “CoMP information IE and/or CoMP hypothesis set IE) (in TS36.423) (or in some variations in a similar form). Here, the CoMPinformation element provides a list of CoMP hypotheses set, each CoMPhypotheses set is a collection of CoMP hypotheses of at least one cell,and each CoMP hypothesis is associated with a benefit metric. The CoMPhypothesis corresponds to PRB-specific resource allocation informationof a hypothesis for a cell. In this case, a separate identifierindicating the allocation of resources for the purpose ofbroadcast/multicast transmission of the Cell B is given to thecorresponding IE (s) or a similar deformed IE, so that thebroadcast/multicast transmission schedule information of the Cell B maybe exchanged with the eNB and/or other cells.

According to the resource allocation related information exchangeprocedure, the broadcast/multicast resources of the Cell B recognized bythe eNB and/or other cells may be recognized as having a high resourceallocation priority (or at a separate priority level).

Advantages of this embodiment over the first embodiment is that, in thecase of the first embodiment, the UE may have to blindly detect the CellB in almost every subframe (i.e., the UE should receive systeminformation of the Cell B at every subframe) and UE complexity (ofcourse, since the UE reads the SIB first in the first embodiment, sothat it may be implemented to detect/read at every PBCH transmissionperiod) is increased.

However, in this embodiment, when the Cell B has broadcast/multicastdata to be transmitted, it transmits transmission schedule informationto the Cell A through X2 signaling in order to inform that. In thiscase, the Cell A provides the partial NW assistance informationgenerated on the basis of the received transmission schedule informationto the UE. Since the UE simply receives the system information of theCell B at a timing indicated by the received partial NW assistanceinformation, UE complexity is significantly reduced. However, in thecase of this embodiment, there may be a disadvantage that X2 signalingmay cause X2 signaling delay of several tens of ms (for example, about20 ms).

Further, when the Cell A informs the transmittable time region (ortransmittable timing) of the system information of the Cell B as thepartial NW tactile information, certain restrictions may be imposed onscheduling of the Cell A in the time region. In this case, the Cell Amay inform the Cell B that the restrictions of the Cell A willnecessarily occur.

For example, when information is exchanged between the Cell A and theCell B through X2 signaling or the like, the Cell A may explicitly orimplicitly, to the Cell B, indicate contents/promise to protectbroadcast/multicast transmission resource (time/frequency/spaceresource) indicated by the broadcast/multicast transmission scheduleinformation delivered by the Cell B, in response. Also, the Cell A mayprovide the partial NW assistance information to the UE as describedabove.

For example, restrictions of the Cell A may be, for example, that atleast the SIB of the Cell A may not be transmitted through thetransmission resource (time/frequency/space) of the SIB of the Cell B.In this case, since the UE simultaneously receives the unicast signaland the SIB from the Cell B through the corresponding transmissionresource, it may be considered that the SIB reception capability fromthe Cell A is transited to the SIB reception capability from the Cell B.Through this operation, the UE may perform the operation of receivingthe broadcast/multicast data by cells considered in the presentinvention even with a single SIB reception capability.

Further, the Cell A provides information (hereinafter referred to as“update information”) about whether or not the update of the SIB of theCell B occurs, as well as information related to the reception timing ofthe system information, as partial NW assistance information, it mayassist the UE receiving the broadcast/multicast data.

That is, when the transmission schedule information is exchanged betweenthe Cell A and the Cell B by X2 signaling, the Cell B may inform theCell A about the update information of the SIB transmitted by the Cell Bthrough backhaul signaling. The Cell A may receive the updateinformation and provide it to the UE. If the received update informationindicates that no updating has occurred in the SIB, the UE maydefine/set an operation so as not to read the SIB of the Cell B at atiming indicated by the received partial NW assistance information.

3. Partial NW-Assistance with SIB Relaying

The present embodiment is an extended embodiment of the secondembodiment. It is proposed that the Cell A receives system information(for example, SIB) directly from the Cell B and relays it to the UE aspartial NW assistance information. Therefore, unlike the case of thesecond embodiment, in this embodiment, since the UE does not need tosynchronize with the Cell B to receive the SIB of the cell B, thecomplexity of the UE is reduced.

For example, the Cell A may transmit the SIB of the Cell Brequested/received from the Cell B instead of the SIB of the Cell A at aspecific SIB transmission timing of the Cell A. In this case, a specificidentifier (cell-ID of the Cell B, for example) may be transmittedtogether so that the UE may know that the currently transmitted SIB isnot the SIB of Cell A but the SIB of Cell B. In this manner, when theSIB of the Cell B is transmitted instead of the SIB of the Cell A, evena terminal having only a single SIB reception capability may receive theSIB of the Cell B, obtaining an effect that there is no need to increasecomplexity of the UE.

In this embodiment, the Cell A may operate in such a manner that theCell A transmits the SIB of the Cell B instead at a timing at which theSIB of the Cell A has not been updated or there is no need to update theSIB of the cell A.

Alternatively, in another example, the operation in which the Cell Atransfers the SIB of Cell B may be performed separately/independentlyfrom the transmission of SIB of the Cell A. For example, thetime/frequency/space resources used for the Cell A to deliver SIB of theCell B may be configured separately/independently from thetime/frequency/space resources used for the Cell A to transmit the SIBof the Cell A. In this case, regardless of whether the SIB of the Cell Ais updated or not, the Cell A may advantageously transmit the SIB of theCell B to the UE immediately when the situation occurs.

In addition to the resources used for transmitting the SIB of the CellA, a common resource pool (not shown) for transmitting SIBs of potentialneighbor cells such as Cell C, D, . . . , and may transmit the SIB of atleast one of the neighbor cells B. C, D, . . . through the correspondingcommon resource pool. In this case, how many SIB(s) of the neighborcells to the maximum level may be delivered at a time may bedefined/configured.

4. Full NW-Assistance

The present embodiment proposes a method in which the UE receivesbroadcast/multicast data from the Cell B, an asynchronous neighbor cell,by fully receiving assistance from the Cell A, a serving cell. In thisembodiment, the Cell A may provide very detailed transmission scheduleinformation for the broadcast/multicast transmission of Cell B so thatthe UE may receive the broadcast/multicast data of Cell B. Compared withthe second and third embodiments, there is a difference in that theassistance information transmitted by the Cell A in order to assist theUE is generated in a very detailed manner up to the DL grant level ofthe Cell B and transmitted to the UE.

That is, the Cell A may transmit specific transmission scheduleinformation regarding the broadcast/multicast transmission of the CellB, as the full NW assistance information to the UE, rather informationto the degree of “read the signal transmitted from the Cell B at aspecific point in time”. To this end, when a specific event such as anaccident occurs and the Cell B transmits an X2 signal to the Cell A, theCell B may provide specific schedule information on the scheduledbroadcast/multicast transmission to the Cell A, and the Cell A maygenerate at least one full NW assistance information (or one-time DLgrant for Cell B information) based on the generated information andtransmit the generated information to the UE.

At this time, the specific schedule information provided by the Cell Bto the Cell A includes broadcast/multicast transmission timinginformation (for example, information as to when to perform thebroadcast/multicast transmission), position information of transmissionresource (time/frequency resource) of broadcast/multicast data, RSconfiguration information for demodulating the broadcast/multicast data,MIMO application information, layer related information, link adaptationrelated information such as MCS, asynchronization related auxiliaryinformation, QCL information, and/or index information of a subframeincluding broadcast/multicast data, and the like.

According to the present embodiment, the UE does not need to receive ordecode the SIB of the Cell B separately, and directly receive and decodethe broadcast/multicast data of the Cell B (for example, For example, abroadcast/multicast (DMRS-based) PDSCH) according to the full NWassistance information received from the Cell A, thereby reducing delayfor signal reception. Therefore, the Cell B should provide all relatedinformation necessary for decoding (for example, includingasynchronization related auxiliary information such as reading 4 msdelayed asynchronous SF boundary) to the Cell A and the Cell A mustdeliver the corresponding information received from the Cell B to the UEas a full NW assistance information, so that the UE may decode thebroadcast/multicast data transmitted from Cell B.

Here, the full NW assistance information may be “one-time DL grant forCell B information”, and here, the reason for the “one-time DL grant” isthat, in order to minimize delay in receiving first information in V2Icommunication, the Cell A first transmits the full NW assistanceinformation to fully assist reception of the broadcast/multicast data ofthe UE, and once the full NW assistance information is transmitted totrigger the V2I, the UE may be defined/configured to receive the SIBform the Cell B (during a specific time interval) according to theembodiment 1. For the time being, the UE will continuouslyreceive/decode the SIB of the Cell B and determine whether the Cell Bwill further perform broadcast/multicast transmission, and thus, the UEis not required to additionally receive the full NW assistanceinformation from the Cell A. In this aspect, the full NW assistanceinformation may be interpreted as one-time triggering DL grant for CellB information. Here, if the UE receives the SIB reception stop requestof the Cell B or a preset time for receiving the SIB of the Cell B hasexpired, the UE may not receive the SIB of the cell B any longer.

FIG. 23 is a flow chart illustrating a method for receivingbroadcast/multicast data of a UE according to an embodiment of thepresent invention. The embodiments described above in connection withthe flow chart may be equally applied. Therefore, redundant descriptionwill be omitted below. Also, the flow chart may be applied to a wirelesscommunication system supporting V2X communication.

First, the UE may receive the broadcast/multicast transmission scheduleinformation (S2310). The broadcast/multicast transmission scheduleinformation is information used for receiving broadcast/multicast datatransmitted from an asynchronous neighbor cell, and includes at leastone of broadcast/multicast transmission timing information of anasynchronous neighbor cell, transmission resource information ofbroadcast/multicast data of the asynchronous neighbor cell, referencesignal (RS) configuration information for demodulating thebroadcast/multicast data, asynchronization related auxiliary informationused for synchronizing with the asynchronous neighbor cell, andquasi-co-locate (QCL) information.

The UE may receive the broadcast/multicast transmission scheduleinformation in various manners according to the embodiment. In anembodiment, the UE may receive the broadcast/multicast transmissionschedule information by receiving system information of the asynchronousneighbor cell including the broadcast/multicast transmission scheduleinformation. Here, the UE may receive the system information of thecorresponding asynchronous neighbor cell directly from the asynchronousneighbor cell or from the serving cell. In an embodiment in which the UEreceives system information from the serving cell, the serving cell maytransmit system information received from the asynchronous neighbor cellto the UE. In another embodiment, the UE may receive thebroadcast/multicast transmission schedule information by receiving a DLgrant including broadcast/multicast transmission schedule information.

Next, the UE may receive broadcast/multicast data from the asynchronousneighbor cell on the basis of the received broadcast/multicasttransmission schedule information (S2320). Here, the broadcast/multicastdata may be transmitted as a physical downlink shared channel (PDSCH)based on a demodulation reference signal (DMRS) from an asynchronousneighbor cell.

In the flowchart, the asynchronous neighbor cell may be determined onthe basis of the result of the RRM measurement. More specifically, theUE may perform RRM measurement such as measurement of reference signalreceived power (RSRP) and measurement of the reference signal receivedquality (RSRQ) by cells, and set a cell having the best RRM measurementvalue as an asynchronous neighbor cell.

General Device to which Present Invention May be Applied

FIG. 24 is a block diagram of a wireless communication device accordingto an embodiment of the present invention.

Referring to FIG. 24, a wireless communication system includes a basestation (BS) (or eNB) 2410 and a plurality of terminals (or UEs) 2420located within coverage of the BS 2410.

The eNB 2410 includes a processor 2411, a memory 2412, and a radiofrequency (RF) unit 2413. The processor 2411 implements functions,processes and/or methods proposed in FIGS. 1 through 29. Layers of radiointerface protocols may be implemented by the processor 2411. The memory2412 may be connected to the processor 2411 to store various types ofinformation for driving the processor 2411. The RF unit 2413 may beconnected to the processor 2411 to transmit and/or receive a wirelesssignal.

The UE 2420 includes a processor 2421, a memory 2422, and a radiofrequency (RF) unit 2423. The processor 2421 implements functions,processes and/or methods proposed in above-described embodiments. Layersof radio interface protocols may be implemented by the processor 2421.The memory 2422 may be connected to the processor 2421 to store varioustypes of information for driving the processor 2421. The RF unit 2423may be connected to the processor 2421 to transmit and/or receive awireless signal.

The memory 2412 or 2422 may be present within or outside of theprocessor 2411 or 2421 and may be connected to the processor 2411 or2421 through various well known units. Also, the eNB 2410 and/or the UE2420 may have a single antenna or multiple antennas.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

An embodiment of the present invention may be implemented by variousmeans, for example, hardware, firmware, software or a combination ofthem. In the case of implementations by hardware, an embodiment of thepresent invention may be implemented using one or moreApplication-Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers and/ormicroprocessors.

In the case of implementations by firmware or software, an embodiment ofthe present invention may be implemented in the form of a module,procedure, or function for performing the aforementioned functions oroperations. Software code may be stored in the memory and driven by theprocessor. The memory may be placed inside or outside the processor, andmay exchange data with the processor through a variety of known means.

It is evident to those skilled in the art that the present invention maybe materialized in other specific forms without departing from theessential characteristics of the present invention. Accordingly, thedetailed description should not be construed as being limitative fromall aspects, but should be construed as being illustrative. The scope ofthe present invention should be determined by reasonable analysis of theattached claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

MODE FOR INVENTION

Various embodiments for implementing the invention have been describedin the best mode for implementing the invention.

INDUSTRIAL APPLICABILITY

The method for assisting communication between UEs in a wirelesscommunication system of the present invention has been described on thebasis of the example applied to the 3GPP LTE/LTE-A system, but thepresent invention may also be applied to various wireless communicationsystems other than the 3GPP/LTE/LTE-A system.

What is claimed is:
 1. A method for receiving, by a user equipment (UE),broadcast/multicast data of an asynchronous neighbor cell in a wirelesscommunication system, the method comprising: receiving, from a servingcell of the UE, first system information of the asynchronous neighborcell non synchronized with the serving cell, wherein the first systeminformation includes schedule information for broadcast/multicasttransmission; and receiving the broadcast/multicast data transmittedfrom the asynchronous neighbor cell, based on the schedule information,wherein the first system information is transmitted by the serving cellinstead of second system information of the serving cell at a specifictransmission timing among transmission timings of the second systeminformation.
 2. The method of claim 1, wherein the broadcast/multicastdata is transmitted in a physical downlink shared channel (PDSCH)related to a demodulation reference signal (DMRS) antenna port from theasynchronous neighbor cell.
 3. The method of claim 2, wherein the DMRSantenna port, and a cell-specific reference signal (CRS) or channelstate information (CSI)-RS is quasi-co-located (QCL)-assumed.
 4. Themethod of claim 1, wherein the schedule information includes at leastone of broadcast/multicast transmission timing information of theasynchronous neighbor cell, transmission resource information ofbroadcast/multicast data of the asynchronous neighbor cell, referencesignal (RS) configuration information for demodulatingbroadcast/multicast data, asynchronization related auxiliary informationused for adjusting synchronization with the asynchronous neighbor cell,and quasi-co-located (QCL) information.
 5. The method of claim 1,wherein the first system information is transmitted through a resourceindependent from a resource in which the second system information istransmitted.
 6. A user equipment (UE) for receiving broadcast/multicastdata of an asynchronous neighbor cell in a wireless communicationsystem, the UE comprising: a radio frequency (RF) unit configured totransmit and receive a radio signal; and a processor configured tocontrol the RF unit, and wherein the UE is configured to: receive, fromthe serving cell of the UE, first system information of the asynchronousneighbor cell non synchronized with the serving cell, wherein the firstsystem information includes schedule information for broadcast/multicasttransmission, and receive the broadcast/multicast data transmitted fromthe asynchronous neighbor cell, based on schedule information, andwherein the first system information is transmitted by the serving cellinstead of second system information of the serving cell, at a specifictransmission timing among transmission timings of the second systeminformation.